Electrum Desktop uses Qt and mobile uses Kivy.
I believe importing custom themes on Desktop would require a lot of refactoring of the source code in order to allow that.
I have some coding experience and am interested in learning Kivy to update the UI to KivyMD.
Not sure how hard it will be, but I believe it wont be that hard.
Does anyone know if there's someone already working on it?
"Electrum KivyMD" doesn't return any hits on Google Search except for this thread so you can take that as a no.
Fortunately, all of Electrum's Qt and Kivy stuff are self-contained in a single folder, so you only have a few files to change.