Can't launch Vanilla Outward from Thunderstore Mod Manager

Hey, I have a friend who has Definitive Edition of the game. However, my other friend and I own the original version of the game. We wanted to play with the Raid Mode mod, however, our friend who owns the Definitive Edition can't get Thunderstore to launch the vanilla version of the game. And he plays Definitive when we're not playing together.

I know this is likely a niche problem, but does anyone know how my friend can get Thunderstore to launch the vanilla version of the game?

We've tried changing what folder Thunderstore uses as the "game files", and still, it will only launch the game with the Definitive version.