[throw0101c]

> Has that always been the case? I have a faint memory of trying once and not being able to with Proxmox 7.x

We did it for 7.x [1] and it worked fine (since upgraded things in-place to 8.x).

[1] https://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_11...