First there was the annoying default “Wine Internet Explorer” for opening images. Why? I found the default source, I deleted it and then it was “Firefox”. Why??? I have different image viewers. Linux distributions are starting to behave like MSW.

Delete local associations:

rm ~/.local/share/applications/wine-*
rm ~/.local/share/applications/mimeinfo.cache

and delete global mime cache

sudo rm /usr/share/applications/mimeinfo.cache

This should work for a while. You will be asked for a new default.