Arch Linux. Always very up-to-date and the AUR is huge. No dealing with PPAs or snaps or flatpaks or appimages. Just paru -S any-software-ever-made
. Also very streamlined (systemd for everything lol) and well documented. I tried NixOS for a bit but it was very inconvenient in comparison and I felt like it was impossible to tinker with or understand if you weren’t good at Haskell. Terrible documentation.
For servers it’s definitely Debian + docker.
I think this is closer to federated Discourse rather than phpBB. Not sure if federation is worth it for forums though.