I use BTRBK and it helped me recover for the early Beta F36 upgrade from F35. It was very fast and easy to restore. I just had problems deleting the problematic snapshot.
You actually have to copy the snapshot from the backup to the pool of subvolumes: sudo btrfs --verbose send /btrfs_pool/_btrbk_snap/root.20220404T1137 | btrfs receive /btrfs_pool/
not sudo btrbk send /btrfs_pool/_btrbk_snap/root.20220404T1137 | btrfs receive /btrfs_pool/root
It will give you four items inside /btrfs_pool/: _btrbk_snap, home, root and a root.20220404T1137.
Then to rename the broken subvolume: sudo mv --verbose /btrfs_pool/root /btrfs_pool/root.broken
Then restore the snapshot as the “new” root: sudo btrfs --verbose subvolume snapshot /btrfs_pool/root.20220404T1137 /btrfs_pool/root
Finally try, now or at a later time, to delete the broken/not wanted one: sudo btrfs --verbose subvolume delete /mnt/btr_pool/root.broken
Thank you for the detailed explanation.
The first command returns the output of:
ERROR: cannot open destination directory /btrfs_pool: Operation not permitted
At subvol /btrfs_pool/_btrbk_snap/root.20220404T1137