I bought a generic N150 based minipc for a firewall & router (running OPNsense), and repurposed an old desktop PC as a server to host immich, paperless, nextcloud, etc… I considered both RPi and mini pc for the server, but I needed a few TB of storage and wanted redundancy. Spinny disks were a much more affordable option than SSDs, and minipcs and Rpis tend to not have much space for those drives. You can add on storage to them, but then they just become clunkier and more expensive than the old PC I already had laying around. Power consumption is probably a few watts higher on the PC than a Pi would be, but it’s not terrible.
That’s why I went the direction I did. I’m 3 about or 4 months in, and it’s been solid so far.
IP ownership isn’t something that you can definitively establish at the outset of a project (even if you copyright code and secure patents for protectable ideas), and wrapping your work in an MIT license won’t preclude infringement claims later on. Plenty of employers sponsor open source work, so it’s not a crazy ask, but it’s usually work that serves the company’s interests. You can ask for permission to work on a project with the mutual understanding that it be MIT licensed, and 2) once work hits a release milestone, get written confirmation from your employer that they grant any claims of ownership to you (or whoever).
If you want more than informal promises from your employer, you’ll find that a spare PC is gonna be much cheaper than the legal consult and drafting of any agreements you or they may want.