there are lots of cheap domain registrar options but if you’re looking for a cheap .com I always go for cloudflare, they also offer .org for pretty cheap and many other options as well. The domains other than the common ones are pretty decently priced as well. I migrated all my domains there last year and it’s really simple, integrates with their DNS really well and payment is pretty streamlined.
Proxmox sounds like it fits their use case , it’s a useful and tweakable solution, and because it’s based on KVM you can pass through hardware with IOMMU. Personally, I run Proxmox on my (admittedly not very good) home server with like 12 gigs of ram and a processor from the early 2010s, handles a few VMs just fine with hardware passthrough to a TrueNAS VM. I do run a lot of my micro services on some cheap thin clients (DNS mainly) for redundancy as I mentioned, they were cheap. Home Assistant OS is happy on Proxmox as is Jellyfin with hardware acceleration.