If you go to the JoiPlay official website, or the patreon(the latest free download post), JoiPlay and its plugins should be listed. The plugins allow more game engines like computer-specific RenPy builds to be available to launch with JoiPlay.
(Went and checked myself. RPG Maker, Ren'Py, Ruffle(Flash), and Godot.)
Though we have no clue what they're building the game with at the moment so we'll just have to wait and see lol.