How to troubleshoot Talk video

Nextcloud version: 27.1.0
Talk Server version: 17.1.0
Custom Signaling server configured: no
Custom TURN server configured: no (had coturn but disabled to go back to basics)
Custom STUN server configured: no
Server OS: Debian 12
PHP version: 8.2 (fpm with apache as webserver)

In case the web version of Nextcloud Talk is involved:
Operating system: Ubuntu 23.04
Browser name and version: Firefox 117 (deb from ppa:mozillateam)

The issue you are facing:
Video calls don’t get established, both parties see themselves and a rotating circle on the other user that they are trying to connect.
At first I was trying this in combination with coturn and devices on different networks (cell hotspot + home network) and since that was not working I reverted to the base case that should work as far as I understand - two devices on the same network.

Is this the first time you’ve seen this error? Y (but it’s the first time I’m trying to use Talk)

Steps to replicate it:

  1. Start video call
  2. Join the call from another device on the same network

The output of your Nextcloud log in Admin > Logging or errors in nextcloud.log in /var/www/:
No spreed related log entries found

The output of your Apache/nginx/system log in /var/log/____:
Based on the apache log it looks like one of the clients is using IPv4 to connect while the other is using IPv6, maybe this is some edge case with dual stack networks, even with IPv6 if one client is coming from link-local (nextcloud is selfhosted on my home network) and the other from one of the other IPv6 blocks stuff is not working

I disabled IPv6 on both test systems and the problem persisted.