I'm using btrfs-sxbackup to create local snapshots. It creates a technical subvolume in
/.sxbackup and creates readonly snapshots in its subfolder. All subvolumes are automatically mounted when OS boots, nothing needed to be specified in fstab.
This one time I tried to restore a snapshot:
btrfs subvol snapshot /.sxbackup/sx-20190308-070926-utc /.before-5.0 btrfs subvol set-default /.before-5.0
Upon reboot the technical subvolume
/.sxbackup/ is not mounted. Now every time I have to mount it manually.