I think I misunderstood what exactly you wanted. I don’t think you’re getting remote GPU passthrough to virtual machines over ROCE without an absolute fuckton of custom work. The only people who can probably do this are Google or Microsoft. And they probably just use proprietary Nvidia implementations.

I believe what you’re looking for is ROCE: https://en.wikipedia.org/wiki/RDMA_over_Converged_Ethernet

But, I don’t know if there’s any FOSS/libre/etc hardware for it.

If you are fine with the slim: US amazon.

I’ve heard good things about used/refurb HP (elite desk and pro desk) and Lenovo (m700 and m900) mini-pcs. A quick search shows they’re going for ~120-140$ for a quad core with 16 gigs of memory.

Check out minisforum, for example this intel mini-pc. They have a ton of selection, not just that one example.

In the LastPass case, I believe it was a native Plex install with a remote code execution vulnerability. But still, even in a Linux container environment, I would not trust them for security isolation. Ultimately, they all share the same kernel. One misconfiguration on the container or an errant privilege escalation exploit and you’re in.

You are not being overly cautious. You should absolutely practice isolation. The LastPass hack happened because one of their engineers had a vulnerable Plex server hosted from his work machine. Honestly, next iteration of my home network is going to probably have 4 segments. Home/Users, IOT, Lab, and Work.

Keep in mind, RAID is fault tolerant, not fault proof. For critical data, keep in mind the 3-2-1 rule. Stored in 3 locations, 2 separate mediums, 1 offsite.