I tried the Mod Manager on a linux distro with Wine and it worked well!
I installed Lutris, installed Diggles from GOG, copied the Mod Manager to the installation directory, duplicated the Diggles starter in Lutris and adjusted the linked .exe file from Diggles.exe to DigglesModManager.exe. It works!!
Only thing is that some icons in the ModManager are not shown correctly. Is this only an issue on Linux?
I guess we should replace those icons/letters somehow and then do a bit more testing.
A documentation on how to use the Mod Manager would be nice. We could even think about registering the ModManager on Lutris. (e.g. like this https://lutris.net/games/vortex-mod-manager/)