btrfs-progs from buster-backports not working after upgrade

Hi!

I mirrored my server disk to vdi files and started them in virtualbox to play around. I also do this to test upgrades. Now I wanted to test BTRFS raid5, because I need an additional pool.

In OMV5 (debian buster) I had latest version 4.20.1 of btrfs-progs. This is very old from 2019. This version is lacking the "raid1c3" and "raid1c4" profiles.

When I install btrfs-progs from backports, it says:

mkfs.btrfs
-bash: /usr/bin/mkfs.btrfs: Datei oder Verzeichnis nicht gefunden

What I am doing wrong? Is there a way to upgrade to buster-backports version and get it working in buster?

seems usrmerge is already installed and also not found in buster-backports.

I am very scared with upgrades. I was happy to have the nice scripts from Dleidert but still there have been bugs which I only found due to testing ahead. So if I want to upgrade, I have to take fresh VDIs and test the whole thing.

Unfortunately there is no upgrade script from dleidert for migration from 5 to 6.