Looking into the PVE 9 Beta with a ver. 3.4.1 PBS co-installed on it I found a prerequisite that leads to a blank how-to for a product that doesn't seem to exist yet.https://pve.proxmox.com/wiki/Upgrade_from_8_to_9#In-place_upgrade
Under "Prerequisites"
"Co-installed Proxmox Backup Server: see the Proxmox Backup Server 3 to 4 upgrade how-to"
This page has the rather useful "There is currently no text in this page." error. The error is text.. so it's too wrong lol.
That's all that is listed however and I can't find any info on PBS 4 either. Does the PVE beta wiki want to suggest PBS v3.4 from v3.3?