Drum map export forget .drm extension on linux

see issue #97976. This is still happening on v3.6.2
Today my first time i did something with a drumset file. Saved the current drumset, and could not load it because the save file did not show up in the file load dialog.

I could see the file in a file manager, and after a search on the internet the manual stated that the file extension has to be .drm. After adding the extension, the file was visible in the load dialog.
Forgive me no to know that I had to add this one to the file name, I have known hundreds of 3 letter file extensions, many of them have several different meanings (like drm).

OS: Ubuntu 20.04.3 LTS, Arch.: x86_64, MuseScore version (64-bit): 3.6.2.548021370, revision: 3224f34