well, they call one of the @privileged (setgroups) because they call https://github.com/coturn/coturn/blob/master/src/apps/relay/mainrelay.c#L2205 https://github.com/coturn/coturn/commit/acbf7e15c9290e0891a6b6b5ce6e81bbaa77ce5a so, for 2 years this exists and it's the reason why it fails. I don't know why it's not failing on TW, maybe libc is not calling the syscall if it's a noop?