I added it as a non steam game to my library. but that does not support remote play together. I also tried through parsec but it just gives remote players control of the host mouse. Would be a huge deal if it did work though.
One of the recent Steamworks SDK versions added a few functions to fetch remote players’ inputs separately, but still they do not simulate Raw Input.
I’ve been working on an extension that automatically wraps majority of Steamworks SDK functions so that calling something esoteric like this doesn’t require messing with C++ - send me an email (and include your GM / Steamworks SDK version numbers) and I’ll get you a copy of it so far.