For anyone like me who donated before it became mandatory (at least I think that’s what is happening in my case), if itch acts like you didn’t pay enough to download the latest version from the game’s page, go to your library instead, find Projekt: Passion there and you will be able to download any prior or current release (0.4, 0.7 or 0.8).
Viewing post in Projekt: Passion 0.8 Release comments
Same problem here. I was able to install 0.7 initially, but now itch only lets me "update" to 0.4. Going to library doesn't help - when clicking on 0.7 or 0.8 the version select defaults back to 0.4 and can't be changed.
I'm guessing in my case it has to with me buying the game for the price with the initial release discount, which is now below the mandatory amount (but that's just wild speculation).