And for the record: I just ran akonadictl fsck on my system (with latest KDEPIM and Qt, so not affected by bug#1173759). It did find 2 unreferenced files in file_db_data, but it successfully *moved* them to file_lost+found, i.e. they no longer existed in file_db_data afterwards. So this seems to be working in general. (unless it is a bug in 20.04.2 that got fixed in 20.08.0, but I don't remember seeing a corresponding change)