FTR, even
> +SystemCallFilter=~@clock @debug @module @mount @raw-io @reboot @swap @privileged @cpu-emulation @obsolete
is not sufficient. From the outer view, TURN server doesn't work (alas can't
tell more from my app). When stracing such a service, it just hangs in the main
thread withing a futex(2) call, apparently all but the main thread exited
(non-trivial amount as logfile contains notion of general relay threads).