“Just” some highly specific VM settings, in the end. I don’t know much about that, and terms like qemu don’t mean anything to me so I followed blog posts until it worked. It’s possible that it is actually trivial.

It’s been a while, but I can look up what I have when you need it. Feel free to ping me!

Yes, it was exactly that: Once I got the NICs set up the way I wanted them it was a breeze and everything just works. And I really like that I made every part work myself, no magic. I learned a lot, and wouldn’t have had I relied on Proxmox fiddling with the right parts for me.