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).
I have similar (on Windows) - I’ve upgraded both my laptop and desktop.
On the desktop all my notebooks have disappeared and been replaced by the original one that Joplin comes with when first installed. All my notebooks appear to still be in my OneDrive folder that I use for cross device synchronisation. @AndreasZiegler - although you have done a sync, are all the notebooks by any chance still in your sync folder?
On the laptop (which also happens to be the last device I used to update my notebooks) I find that they are still there, with a banner about needing to upgrade the sync target (which I haven’t clicked yet), so I have done a JEX export on there so at least I will be able to restore.
I also opened Joplin on my Android phone (the version on there is 1.0.339) and it successfully synced with my notes (and the last one I edited is correct).
Should I just go ahead accept the link on updating my sync target on the laptop? What is it going to do?
How do I best recover the Notebooks on my desktop? Answer: Ooops - I had moved my Joplin database to a different partition on my hardrive and changed the launch shortcut, but that the shortcut got replaced when updated!