ResidualVM is a sister project of ScummVM. It allows you to play to games which are not (and probably never) supported by ScummVM. For instance, the games using the GrimE game engine. Three games are currently compatible with this emulator: Grim Fandango, Escape from Monkey Island and Myst III - Exile.
ResidualVM has been added as a second emulator of ScummVM system. The switch between ScummVM and ResidualVM is automatic. Indeed, the way to add new games is the same as for ScummVM. The only difference is the file extension to use. Once your game inside the
/recalbox/share/roms/scummvm folder, you have to name your shortcut file as gameShortName.residualvm instead of gameShortName.scummvm (for example grim.residualvm to add Grim Fandango). Recalbox will automatically select and use the right emulator.
If you need more information about this new emulator, please read the ResidualVM documentation.
You will find the complete compatibility list on the ResidualVM site.
But note that, for the moment, Escape from Monkey Island stuck after the introduction on RPI plateforms.