You need amds proprietary ROCM driver which supports stuff like ai. However i already had issues setting up anything ai on my desktop fedora system, steam deck uses an immutable fs and afaik it gets reset after every update. If doing it on a desktop pc is hard then doing it on the deck will be like walking on lego. Good luck soldier.
Option 2 would be your best bet. Great balance between security and convenience. Bitwarden is my go to because afaik it stores every detail encrypted (unlike mainstream PWs) and when you open your vault, the database gets transferred to your pc and is decrypted locally. Its essentially the same as option 1, just 1000x more convenient.
Id only selfhost vaultwarden if you want bitwardens premium features, if you dont then youre maintaining a service which you wouldnt really need. Not to mention if you selfhost on a machine on your network, you have to deal with exposing that machine to the internet, not really worth it imo.
From every diffusion github ive seen, they all seem to have instructions for ubuntu, so that may be your easiest bet. Same with rocm, it seems easier to install on ubuntu than other distros. Especially fedora…