For the sake of anyone who finds this looking for a proper answer, SteamOS/Bazzite/ChimeraOS are all suitable for this purpose. I didn’t consider them when writing this because I thought they were primarily game focused, but for non-games like Jellyfin or a web browser, you can just add them to your steam library as non-steam games.
As others have said, debian is very minimal, so If you would prefer to setup and configure the whole system yourself, debian is a good choice.
Personally, I prefer fedora server. It comes with more things configured out of the box (zram and sysctl configs for example) as well as better security defaults (selinux included with proper policies) and first class support for container infrastructure. Ultimately you could achieve a similar end result with debian, but for my homeservers I prefer to let the fedora team handle most of the system configuration for me.