Hi guys, I saw your game and spoke to you briefly today at Gamebridge. It turns out you were right and my notion of local-co-op-over-network is just Steam Remote Play streaming. I must have imagined or hallucinated an exchange with someone because I can't find any mention of a non-video-streaming method of doing it. My delusions aside apparently remote play is better than it used to be and it might work better than expected.
Although mechanically it is very different, if you have not seen it, 'Path of Achra' (https://ulfsire.itch.io/path-of-achra) might be worth a look for the writing, which is a Bronze Age pastiche. If you know anyone who lives in a big college town studying literature you might attract some interest in giving the game some texture through the writing, whether that is in text-based 'barks', item descriptions, procedurally generated room descriptions and so on. It looks like a promising project, so hats off for getting it this far so far.
James.