Check out used tiny/mini/micro desktops on eBay. Loads of info here: https://www.servethehome.com/introducing-project-tinyminimicro-home-lab-revolution/

Only downside is going to be no GPU for the AI workload. Maybe some of the later AMD APUs could cut it. If not, all three major manufacturers have SFF variants that are pretty much the same hardware in a little bigger case. Those will accept smaller off the shelf GPUs.

Vaultwarden is pretty game changing. No more reusing passwords and they aren’t in the cloud.