I don't think Github has DMs.

From what I understand of STUN and TURN, there is absolutely no point running STUN an TURN on the same server as Nextcloud - if you do, you could just as well skip running them in the first place. STUN and TURN only help if they are on a dedicated box, as close to a internet root server as possible, ideally in a big datacenter somewhere on the internet backbone. They can't be behind firewalls and layers of routers...

So your performance will already improve if you delete your local STUN and TURN and use the Nextcloud STUN as our free STUN runs in a big data center. Then you have to find a TURN somewhere that you can run also close to the backbone, or try using without...

Yes, running STUN and TURN properly is a pita.

I'm no super expert so check what I'm saying, but this is based on my best understanding of what these do and I had to write our documentation for customers about our Spreed High Performance Backend which, among other things, does STUN and TURN ;-) (Nextcloud marketing dude here)

I reached out on to your IRC. I'll help, if I can.