LATEST UPDATE:
Refer to Post #3 below.

This error sometimes happens on my system after an update, if some of you have noticed:
https://forum.obarun.org/d/1584-solved-cant-startx-and-sent-back-to-tty-terminated-successfully

As a recap, my system is set up as a password-less autologin into XFCE.
Upon updating my system, I am stuck at the tty (but already logged in automatically).
Executing "startx" causes an Xorg error that displays "Server terminated successfully (0)".

As a side note, this error may not be related to the new 66 version.
This is because this has happened as early as November 23, Saturday.
I did not report it immediately as I hoped some random update somewhere will fix it.
The lack of a usable system has been circumvented by rolling back my system with Timeshift at the tty each time.
My 66 is on version 0.7.2.1-2, and upgrading to 0.8.0.0 previously, and now 0.8.0.1-1, has caused the same error irregardless.

"# 66 tree resolve Master ":

name        : Master
allow       : hyperspace
current     : None
contents    : global
nallow      : 1
ncontents   : 1
rversion    : 0.8.0.1

"% 66 tree resolve Master":

name        : Master
allow       : root
current     : None
contents    : session boot global
nallow      : 1
ncontents   : 3
rversion    : 0.8.0.1

"# 66 -z tree status -g":

Name        : global
Current     : no
Enabled     : yes
Allowed     : hyperspace
Groups      : user
Depends     : \
              └─None
Required by : \
              └─None
Contents    : \
              ├─pulseaudio-log (pid=1128, state=Enabled, type=classic, tree=global)
              ├─dbus@hyperspace-log (pid=1130, state=Enabled, type=classic, tree=global)
              ├─xdg-user-dirs (pid=up, state=Enabled, type=oneshot, tree=global)
              ├─pulseaudio (pid=1874, state=Enabled, type=classic, tree=global)
              └─dbus@hyperspace (pid=1137, state=Enabled, type=classic, tree=global)

"% 66 -z tree status -g":

Name        : boot
Current     : no
Enabled     : no
Allowed     : root
Groups      : boot
Depends     : \
              └─None
Required by : \
              └─None
Contents    : \
              ├─boot@system:system-hostname (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-run (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-tmp (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-proc (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-sysctl (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:udevd-log (pid=357, state=Enabled, type=classic, tree=boot)
              ├─boot@system:tty-earlier@tty12 (pid=274, state=Enabled, type=classic, tree=boot)
              ├─boot@system (pid=up, state=Enabled, type=module, tree=boot)
              ├─boot@system:populate-run (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:populate-tmp (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-sys (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:populate-sys (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-dev (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-pts (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-shm (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:populate-dev (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-cgroups (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-branch (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-hwclock (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:modules-kernel (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-random (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:modules-system (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:udevd (pid=539, state=Enabled, type=classic, tree=boot)
              ├─boot@system:udevadm (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-fontnkey (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-fsck (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-fstab (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:system-branch (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-rw (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-authfiles (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-sethostname (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-loop (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-time (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-tmpfiles (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:mount-netfs (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-dmesg (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:local-branch (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:runtime-branch (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:canopy (pid=up, state=Enabled, type=oneshot, tree=boot)
              ├─boot@system:tty-rc@tty1 (pid=1051, state=Enabled, type=classic, tree=boot)
              └─boot@system:tty-rc@tty2 (pid=1052, state=Enabled, type=classic, tree=boot)

Name        : global
Current     : no
Enabled     : yes
Allowed     : root
Groups      : admin
Depends     : \
              └─None
Required by : \
              └─session (Enabled)
Contents    : \
              ├─dbus-log (pid=920, state=Enabled, type=classic, tree=global)
              ├─networkmanager-log (pid=921, state=Enabled, type=classic, tree=global)
              ├─consolekit-log (pid=922, state=Enabled, type=classic, tree=global)
              ├─openntpd-log (pid=923, state=Enabled, type=classic, tree=global)
              ├─dbus (pid=930, state=Enabled, type=classic, tree=global)
              ├─openntpd (pid=931, state=Enabled, type=classic, tree=global)
              ├─networkmanager (pid=944, state=Enabled, type=classic, tree=global)
              └─consolekit (pid=943, state=Enabled, type=classic, tree=global)

Name        : session
Current     : no
Enabled     : yes
Allowed     : root
Groups      : admin
Depends     : \
              └─global (Enabled)
Required by : \
              └─None
Contents    : \
              ├─boot-user@hyperspace:mount-run@hyperspace (pid=up, state=Enabled, type=oneshot, tree=session)
              ├─scandir@hyperspace (pid=up, state=Enabled, type=module, tree=session)
              ├─scandir@hyperspace:setenv@hyperspace (pid=up, state=Enabled, type=oneshot, tree=session)
              ├─scandir@hyperspace:svscan@hyperspace-log (pid=1004, state=Enabled, type=classic, tree=session)
              ├─boot-user@hyperspace (pid=up, state=Enabled, type=module, tree=session)
              └─scandir@hyperspace:svscan@hyperspace (pid=1025, state=Enabled, type=classic, tree=session)

"/run/66/log/0/current":

2024-12-21 14:22:55.327186442  66-execute: info: Starting service: boot@system:tty-earlier@tty12
2024-12-21 14:22:55.328782291  [Start services of tree boot...]
2024-12-21 14:22:55.330456517  start: info: Initialized successfully: boot@system
2024-12-21 14:22:56.340009772  signal: info: Initialized successfully: boot@system:system-hostname
2024-12-21 14:22:56.340015354  signal: info: Initialized successfully: boot@system:mount-run
2024-12-21 14:22:56.340032209  signal: info: Initialized successfully: boot@system:populate-run
2024-12-21 14:22:56.340033914  signal: info: Initialized successfully: boot@system:mount-tmp
2024-12-21 14:22:56.340041633  signal: info: Initialized successfully: boot@system:populate-tmp
2024-12-21 14:22:56.340069911  signal: info: Initialized successfully: boot@system:mount-proc
2024-12-21 14:22:56.340072201  signal: info: Initialized successfully: boot@system:mount-sys
2024-12-21 14:22:56.340087874  signal: info: Initialized successfully: boot@system:populate-sys
2024-12-21 14:22:56.340102987  signal: info: Initialized successfully: boot@system:mount-dev
2024-12-21 14:22:56.340117884  signal: info: Initialized successfully: boot@system:mount-pts
2024-12-21 14:22:56.340132272  signal: info: Initialized successfully: boot@system:mount-shm
2024-12-21 14:22:56.340146728  signal: info: Initialized successfully: boot@system:populate-dev
2024-12-21 14:22:56.340161385  signal: info: Initialized successfully: boot@system:mount-cgroups
2024-12-21 14:22:56.340175820  signal: info: Initialized successfully: boot@system:mount-branch
2024-12-21 14:22:56.340190622  signal: info: Initialized successfully: boot@system:system-hwclock
2024-12-21 14:22:56.340205012  signal: info: Initialized successfully: boot@system:modules-kernel
2024-12-21 14:22:56.340220104  signal: info: Initialized successfully: boot@system:system-random
2024-12-21 14:22:56.340234791  signal: info: Initialized successfully: boot@system:modules-system
2024-12-21 14:22:56.340249321  signal: info: Initialized successfully: boot@system:system-sysctl
2024-12-21 14:22:56.340270995  signal: info: Initialized successfully: boot@system:udevd-log
2024-12-21 14:22:56.340290298  signal: info: Initialized successfully: boot@system:udevd
2024-12-21 14:22:56.340304799  signal: info: Initialized successfully: boot@system:udevadm
2024-12-21 14:22:56.340319545  signal: info: Initialized successfully: boot@system:system-fontnkey
2024-12-21 14:22:56.340333793  signal: info: Initialized successfully: boot@system:system-fsck
2024-12-21 14:22:56.340348582  signal: info: Initialized successfully: boot@system:mount-fstab
2024-12-21 14:22:56.340363443  signal: info: Initialized successfully: boot@system:system-branch
2024-12-21 14:22:56.340378934  signal: info: Initialized successfully: boot@system:mount-rw
2024-12-21 14:22:56.340394052  signal: info: Initialized successfully: boot@system:local-authfiles
2024-12-21 14:22:56.340408336  signal: info: Initialized successfully: boot@system:local-sethostname
2024-12-21 14:22:56.340422965  signal: info: Initialized successfully: boot@system:local-loop
2024-12-21 14:22:56.340437525  signal: info: Initialized successfully: boot@system:local-time
2024-12-21 14:22:56.340452791  signal: info: Initialized successfully: boot@system:local-tmpfiles
2024-12-21 14:22:56.340467648  signal: info: Initialized successfully: boot@system:local-dmesg
2024-12-21 14:22:56.340482411  signal: info: Initialized successfully: boot@system:mount-netfs
2024-12-21 14:22:56.340497021  signal: info: Initialized successfully: boot@system:local-branch
2024-12-21 14:22:56.340511554  signal: info: Initialized successfully: boot@system:runtime-branch
2024-12-21 14:22:56.340526019  signal: info: Initialized successfully: boot@system:canopy
2024-12-21 14:22:56.340546033  signal: info: Initialized successfully: boot@system:tty-rc@tty1
2024-12-21 14:22:56.340564454  signal: info: Initialized successfully: boot@system:tty-rc@tty2
2024-12-21 14:22:56.349370727  66-execute: info: Starting service: boot@system:udevd-log
2024-12-21 14:22:56.351551089  signal: info: Successfully started service: boot@system:udevd-log
2024-12-21 14:22:56.354172033  signal: info: Successfully started service: boot@system:mount-proc
2024-12-21 14:22:56.354331036  signal: info: Successfully started service: boot@system:mount-run
2024-12-21 14:22:56.356122723  signal: info: Successfully started service: boot@system:system-sysctl
2024-12-21 14:22:56.356889607  signal: info: Successfully started service: boot@system:system-hostname
2024-12-21 14:22:56.359168961  signal: info: Successfully started service: boot@system:mount-tmp
2024-12-21 14:22:56.363347630  signal: info: Successfully started service: boot@system:mount-sys
2024-12-21 14:22:56.366710788  signal: info: Successfully started service: boot@system:populate-run
2024-12-21 14:22:56.368545681  signal: info: Successfully started service: boot@system:populate-tmp
2024-12-21 14:22:56.372278220  signal: info: Successfully started service: boot@system:mount-dev
2024-12-21 14:22:56.384057765  signal: info: Successfully started service: boot@system:mount-shm
2024-12-21 14:22:56.385095305  signal: info: Successfully started service: boot@system:mount-pts
2024-12-21 14:22:56.385632859  signal: info: Successfully started service: boot@system:populate-dev
2024-12-21 14:22:56.387797578  signal: info: Successfully started service: boot@system:populate-sys
2024-12-21 14:22:56.441106363  signal: info: Successfully started service: boot@system:mount-cgroups
2024-12-21 14:22:56.446912086  signal: info: Successfully started service: boot@system:mount-branch
2024-12-21 14:22:56.456840697  signal: info: Successfully started service: boot@system:system-random
2024-12-21 14:22:56.469625387  signal: info: Successfully started service: boot@system:system-hwclock
2024-12-21 14:22:56.647565202  signal: info: Successfully started service: boot@system:modules-kernel
2024-12-21 14:22:57.449814262  signal: info: Successfully started service: boot@system:modules-system
2024-12-21 14:22:57.663308659  signal: info: Successfully started service: boot@system:udevd
2024-12-21 14:22:58.805760351  signal: info: Successfully started service: boot@system:udevadm
2024-12-21 14:22:58.829661393  signal: info: Successfully started service: boot@system:system-fontnkey
2024-12-21 14:22:58.852310108  signal: info: Successfully started service: boot@system:system-fsck
2024-12-21 14:22:58.859804557  signal: info: Successfully started service: boot@system:mount-fstab
2024-12-21 14:22:58.865478536  signal: info: Successfully started service: boot@system:system-branch
2024-12-21 14:22:59.020091725  signal: info: Successfully started service: boot@system:mount-rw
2024-12-21 14:22:59.030386795  signal: info: Successfully started service: boot@system:mount-netfs
2024-12-21 14:22:59.033090952  signal: info: Successfully started service: boot@system:local-time
2024-12-21 14:22:59.033148528  signal: info: Successfully started service: boot@system:local-authfiles
2024-12-21 14:22:59.036258963  signal: info: Successfully started service: boot@system:local-sethostname
2024-12-21 14:22:59.036503824  signal: info: Successfully started service: boot@system:local-loop
2024-12-21 14:22:59.162209543  signal: info: Successfully started service: boot@system:local-tmpfiles
2024-12-21 14:22:59.176854053  signal: info: Successfully started service: boot@system:local-dmesg
2024-12-21 14:22:59.183103588  signal: info: Successfully started service: boot@system:local-branch
2024-12-21 14:22:59.221551940  66-execute: info: Starting service: dbus-log
2024-12-21 14:22:59.221614612  66-execute: info: Starting service: consolekit-log
2024-12-21 14:22:59.221672652  66-execute: info: Starting service: networkmanager-log
2024-12-21 14:22:59.221849574  66-execute: info: Starting service: openntpd-log
2024-12-21 14:23:00.228732609  66-execute: info: Starting service: scandir@hyperspace:svscan@hyperspace-log
2024-12-21 14:23:00.288478602  signal: info: Successfully started service: boot@system:runtime-branch
2024-12-21 14:23:00.294752217  signal: info: Successfully started service: boot@system:canopy
2024-12-21 14:23:00.297919881  signal: info: Successfully started service: boot@system:tty-rc@tty2
2024-12-21 14:23:00.297937005  signal: info: Successfully started service: boot@system:tty-rc@tty1
2024-12-21 14:23:00.298307838  signal: info: Successfully started service: boot@system
2024-12-21 14:23:00.298640779  tree: info: Successfully started tree: boot
2024-12-21 14:23:00.299820881  66-execute: info: Starting service: boot@system:tty-rc@tty2
2024-12-21 14:23:00.299892773  66-execute: info: Starting service: boot@system:tty-rc@tty1