That was very easy. I now tried that, but my page is still not accessible, but at least I have a different output in the logs now:
root@<vps-hostname>:/var/discourse# docker container logs <container-id>
run-parts: executing /etc/runit/1.d/00-ensure-links
run-parts: executing /etc/runit/1.d/00-fix-var-logs
run-parts: executing /etc/runit/1.d/anacron
run-parts: executing /etc/runit/1.d/cleanup-pids
Cleaning stale PID files
run-parts: executing /etc/runit/1.d/copy-env
Started runsvdir, PID is 38
ok: run: redis: (pid 48) 0s
ok: run: postgres: (pid 46) 0s
chgrp: invalid group: ‘syslog’
rsyslogd: imklog: cannot open kernel log (/proc/kmsg): Operation not permitted.
rsyslogd: activation of module imklog failed [v8.1901.0 try https://www.rsyslog.com/e/2145 ]
supervisor pid: 51 unicorn pid: 76