Gawd that is a hell of a ride. Very interactive. I"ve done the in-place upgrade on about 8 servers now. Frequent surprises.
(Chickin pic tangentally related.)
I backed up my homelab, upgraded PBS, and I'm watching PVE upgrade now.
That's the first one I've upgraded without evacuating it first.
It's a bumpy ride, but looks like I'm getting there.
For anyone that hasn't seen the article ...
https://pve.proxmox.com/wiki/Upgrade_from_8_to_9