Not OP, and I don't use proxmox, but in my case the host is just another client of the router. Of course, if the router is borken for whatever reason, the host won't get any updates. But if that's the case, upgrading the host is unlikely to be my top priority.

If I really need to update the host with no router: I plug my iPhone via USB, and I'm off to the races.

I will write another blog post about it eventually. Proxmox is connected to the network via additional external NIC at the moment.

Please do a Show HN when you are done.