I updated Joplin on my Mac OS X to the following version
Joplin for Desktop
Copyright © 2016-2020 Laurent Cozic
Joplin 1.0.245 (prod, darwin)
Client ID: b00f19c0548343179ab1416fe112740f
Sync Version: 2
Profile Version: 33
Keychain Supported: Yes
Revision: 2aa7eaa (master)
After the update I synced. The sync took quite long compared to what I’m used to. At the end of the sync all my notebooks (except on sub-notebook) were gone as well as my tags (except one). Some of my notes are now under “All notes” and under “conflicts” but I assume this are not all my notes.
The notes under “All notes” seems to have the right notebook (the symbol right to the forward button).
The same happened to my Joplin under Linux.