Thank you again for all your help ! You really went above and beyond to help me figure this out, and I genuinely appreciate the time and effort you put into testing everything!
My friend had actually tested after I had re-added the demo, but that’s fine, it’s definitely better to have everything set up cleanly anyway.
To make things as clear as possiblef for anyone who might run into the same issue, the key is simply to mark the game as paid (check the “this is a paid game” box). Once that’s done, a new checkbox appears in the uploaded files section where you can mark one of the files as a free demo. That’s what fully solves the problem.
Thanks again for your patience and all the help, seriously appreciated!