I have now spun up arm64 proxmox on a hetzner ampere root server (cpu=80) using this port
https://github.com/jiangcuo/Proxmox-Port - with a debian bookwork base and pve8
In the main it works well and will keep it running for my workload.
I have raised two issues that I have found on their github - one is kvm crashing when using novnc to view the console; not sure if this is an upstream issue - I found the segfault is in a library that ships with debian.
The second is the kernel is not built with the br_netfilter module, but inserting that makes the firewall work.
Otherwise I have 10x vms up and running and everything seems stable
I really would love to see an official proxmox distribution for this architecture!