SOLVED: Jellyfin client is unable to connect to the server after a server upgrade

[scotrod]

Greetings,

Today I've upgraded my Jellyfin server (docker container on top of Ubuntu VM). After that, the Jellyfin client installed on my Android TV box is not able to connect to the server. Autodiscovery is not working. The rest of my Jellyfin clients (on phone, PC, etc) are not having issues.

I've tried to:
 - Reboot the Android TV box;
 - Check FW rules (pfsense FW is allowing the connections and I see that in the FW logs);
 - Reinstall the Jellyfin App;
- Disabling UFW on Ubuntu;
- Going back to the older Jellyfin server version (10.10.1);
 - Restart the Jellyfin Server docker container & Ubuntu host itself;
 - I don't have a native browser on that Android TV box so I can't access the Jellyfin URL without the native app;

Jellyfin server version:
10.10.7

Android TV box Jellyfin client:
jellyfin-androidtv 0.18.10 release

Now here is the funny part: I can't see the problematic box's IP or hostname in the Jellyfin server logs - it's like it's not even reaching the Jellyfin server. That means that I should search the fault at L2 or Ubuntu, which doesn't make any sense - this problem appeared after I upgraded the server. Any help would be appreciated.

[scotrod]

It was a frickin docker problem - upon updating the rest of my containers some of em took a large chunk of VLANs - one of which included my home IoT VLAN under which the android box was sitting in... More info here:
https://www.linuxquestions.org/questions...ts-819880/