Okay, so I made the folder and copied lib/monogame.framework.desktopgl.core/3.7.0.7/lib/netstandard2.0/MonoGame.Framework.dll
to lib/netstandard2.0/MonoGame.Framework.dll
(I assume editing the manifest would also have worked), and now the game seems to run fine, except I still get these errors on launch:
AL lib: (WW) GetProcPath: Failed to readlink /proc/self/file: No such file or directory
AL lib: (WW) alc_initconfig: Failed to initialize backend "jack"
Not sure if those are significant. The game does have sound.