could you ./launcher enter app and
ulimit -u
this shows the maximum number of user processes/threads allowed
ulimit -a
this shows all resource limits
cat /sys/fs/cgroup/pids.max
This checks the maximum number of processes (PIDs) allowed for the container or system cgroup.
now use logout to return to the host;
systemctl show docker | grep TasksMax
this checks whether systemd has imposed a task/thread limit on the Docker service.
systemctl show containerd | grep TasksMax
this does the same kind of check, but for the containerd service instead of Docker directly.
docker inspect app | grep -i pid
this checks the process / PID limits and settings of your Discourse container. The grep -i pid: filters to anything containing “pid” (case-insensitive).
If you keep getting errors, please could you paste the output of these commands here, that would be helpful.