I have a usb drive that I plugged in physically in my Macbook and used quite a while to backup my Mac OS X system. The backup folder was called Backups.backupdb.
Recently, I attached this to a Raspberry Pi (HFS+, journalled) and wanted to back it up again. But now it's backing up as <my_computer_name>.backupbundle. I used this tutorial to achieve that: https://alexdunn.io/posts/rpi_time_machine/ (the only difference: I used Raspbian, and had to explicitly create a samba user).
I thought Time Machine would be able to recognize that it already has my system backed up on it, but it didn't.
How do I get Time Machine to recognize that I already have my old backups on there?
Edit: there seems to be a similar question here Time Machine on a local drive, then make that drive a network drive (via Server.app) on a different computer
But it didn't give the answer, this is in part, I believe, because Catalina has a new extension (.backupbundle) and because smb is now the prefered protocol.