ok happy to see that you solved your issue.
i think pacman was complained about s6-boot installed concerning creation of s6log user, right?
Anyway, i will explain for other people which can have the same issue.
first be sure that the log group have the correct gid. The log group need to be set at 19 like this :
$ cat /etc/group
$ log:x:19:
if it's not the case, change the gid by :
$ sudo groupmod -g 19 log
be sure that the s6log user exist, if it's not , create it :
$ sudo useradd -u 19 -g 19 -d / -G log -c "S6 log user" -s /usr/bin/nologin s6log
then give the correct owner for /etc/s6/boot-serv/uncaught-logs, /var/log/s6rc, /var/log/s6serv diretories like this:
$ sudo chown s6log:log /etc/s6/boot-serv/uncaught-logs
$ sudo chown s6log:log /var/log/s6rc
$ sudo chown s6log:log /var/log/s6serv
then reboot, this should resolv the trouble.
ps: @ then spent some hours getting my head around s6opts big_smile ...somewhat less straightforward than runit...
the wiki page for s6opts coming soon here : wiki.obarun.org.... i have some trouble to solve for the main site then i take care about all wiki page ... a little more patience please ;)