Hey Casper!
I ended up finding out what my problem was. The policy I had mentioned
trying in my first post ended up being correct after all. It turned out
that I had a rogue ejabberd policy in the system in addition to the
policy I was testing, and the rogue policy had higher priority than the
one provided by the RPM ☹
I must have installed this policy by hand some time in the past and
forgotten to remove it. After removing it, I found that I just needed
one more line on the policy to address this issue:
https://src.fedoraproject.org/rpms/ejabberd/c/d48066216cac7e2ec1626d65376...
With this policy I am able to run ejabberd with STUN/TURN enabled and
with the nis_enabled bool disabled.
There are updates for F33-36 in Bodhi now:
https://bodhi.fedoraproject.org/updates/?packages=ejabberd