Funny observation: The Steam version of the game contains an ISO file called GK1.GOG
I had better results (menu music not messed up) by extracting that ISO into a directory and pointing ScummVM at it, than just pointing ScummVM at the GK1 directory.
The 20th Anniversary Edition uses a completely different engine (Unity I believe) and is 3D. So the chances of it being supported by ScummVM one day are rather slim (I don't want to write 'never' as this might come back to bite me in a few decades :-; ). It would more be within the scope of ResidualVM, but I would not expect it to be supported there anytime soon either.