@NameLessGO I updated it to version 2.11 and tried again. but the .db file is the same, so there was no difference. also exporting a deck from the new version and trying to import it in Anki gave same error.
@Danika_Dakika yes, I looked at all topics about Mnemosyne and they didn’t apply as I have a different error (Issue importing Mnemosyne cards into Anki and Error importing mnemosyne cards to anki) or were about importing issues related to media import
The export from Mnemosyne is a .cards file but when you rename it to .zip, you can see that it just contains a .xml file (and metadata, and optionally media files) which contains the learning data. or the .db file from Mnemosyne contains learning data as well.