In my setup, it's the same, my OPNsense is a guest running on the Proxmox VE instance.
Is the "upgrade without guests running" a new prerequisite with the PVE 8.0? In the past I did all the upgrades (7.0 to 7.1, 7.1 to 7.2, 7.2 to 7.3, 7.3 to 7.4) with the OPNsense VM running and I haven't...