It seems possible to just move away the unwanted backups and re-linking the
Latest directory. A few things to know about TM first:
- It uses directory hard links, which are kind of black magic
- It's super fragile, and once this is done, I would format the disk and start backing up from scratch
Now, the finder is ""smart"" and tries to block the user from modifying TM backups by hand. Also the terminal does the same, so no luck. The first thing to do is to rename the backup folder so they don't think it's TM anymore:
cd /Volumes/Time\ Machine # or your disk name
mv Backups.backupdb Backups.backupdb_1
Now the folder is unprotected. You can move the unwanted backups to the parent directory (do NOT delete them), with the finder or the terminal.
Make sure to also move away the "in progress" backup and the
Latest folder. You'll need to re-create it with the terminal, it's a soft link:
ln -s 2021-[the latest backup] Latest
Do not include any trailing slash, I'm not sure if this step is sufficient alone to restore from a previous backup, it's worth trying out.
Once this is done, to verify that the correct backup is loaded, check the date shown by the migration assistant.