From what I understand, while OpenBSD is currently not accepting LLM contributions, they mostly made that choice out of legal copyright concerns, and seem like they would jump on the bandwagon when they consider it to be safer legally.

NetBSD is also worth a look, especially with the MicroVM kernel stuff in 11. You can look at smolBSD to start playing with it immediately.

It's a desktop, there should be sufficient space to fit more than one drive. You can also use external drives. I use three on my server.