During install, I apparently forgot to double check the formats of the partitions.
the root ‘/‘ partition is Btrfs and it is saving a snapshot every time I boot.
Can I reformat in YaST partitioner to EXT4, mounting it as ‘/‘ without destroying the root directories?
NO…
You can turn snapper off in Yast
I have recently ‘moved’ the root partition on a couple of machines from BTRFS to Ext4 on new drives. (SSD/NVMe)
So if you had a spare drive you could temporarily move ‘/’ to the spare drive, change your original drive to Ext4 and then move ‘/’ back.
I ‘moved’ ‘/’ with a live distro. There is a bit of a process I went through.
Interestingly when the BTRFS partition was mounted with the live distro it incorrectly showed /opt and /srv to be empty and hence they were not copied, I had to copy them from the booted original BTRFS partition. So before you reformat the original drive, make certain that you have all the files transferred to the new/temporary drive.
You possibly failed to mount the subvolumes.
Possibly, not sure why this only occurred on 1 of the 2 machines, but I suppose the take-away for me was to verify you have everything copied and operational before wiping the original if you take this path.