The easiest way I found to set a Mime Type handler in Linux is the following:
- Create a .desktop file for a handler application, in "/home/alen/.local/share/applications". Make sure that the MimeType is set in the .desktop file.
- Open Dolphin (KDE file browser), select a file you want to handle, right-click it and select Properties. Next to Type, click the wrench icon to open file type editor (KEditFileType). Set the handlers there (add, edit, remove, or set preference order).
This setting has effect on the whole system so Mime Type handler preference order will be reflected in other file browsers (Nemo, Nautilus, etc.).