You can use the FiltaQuilla extension to add content-type as search category. It’s a pretty powerful yet straight forward extension

Last stable version is over 7 years old. Ouch…

If your main motivation is never going through that kind of digital loss, please please please do yourself a favor and do not rely solely on a local solution. If there’s a fire in your apartment, the best nextcloud setup isn’t going to do shit for you. Look up the 3-2-1 rule if you want to be safe.

It’s a little hard to decipher what you mean. I think I understood that you basically want to have a headless gaming rig so you can stream your games in the rest of your network. The closest you would get is probably Bazzite, and configure it to directly boot into steam big picture mode so you can use steam link on your connecting devices. If you would like a platform agnostic setup you could look into sunshine. That will involve more tinkering tho.