@rmlazzari
You need the 'mono' framework installed to run .net applications on Linux. I think the package name is 'mono-complete' on Ubuntu based distributions.
After that you can run it with
Code:
$ mono /path/to/gMKVExtractGUI.exe
But .net applications sometimes look artifical or broken on Linux, on hi-dpi displays mostly unusable.
Alternatives are:
https://forum.ubuntu-fr.org/viewtopic.php?id=1508741
(post is in french but installation instructions are easy to spot)
or:
https://www.videohelp.com/software/Inviska-MKV-Extract
(seems abandoned, developers website is dead)