Any tips or specific intricacies of using lutris on NixOS with externally mounted drives?

Having a little trouble here with getting lutris to work with externally mounted drives.

I’m attempting to run Ghost Recon: Breakpoint through the ubisoft store, and whilst I already have the game downloaded and installed on my external drive, I can’t seem to get ubisoft store to recognise that the drive exists.

Am I missing something completely obvious?

I like to use bind mounts so that it’s transparent to the program in question.