This isn't a question but rather the answer to a problem I didn't found anything about.

For this version (not the remastered), the game runs great on Steam Deck but you may suddenly run into visual issues. Specifically the first time you go to Blackwell Academy, where David drops you off. As soon as you see the fountain, it may be covered in white artifacts spiking around. Different proton version don't do anything, changing the ingame settings doesn't fix this either.
Solution: Turn off Half Rate Shading in Steam Deck performance&battery options. Then the game will be free from visual glitches on Steam Deck.

You shouldn't really use Half Rate Shading anyway, as the battery time increase is marginally but it decreases image quality in a lot of games heavily, text is often unreadable and you get strange visual bugs like this. But I still wanted to make this thread, for the case anyone else runs into this issue and doesn't suspect Half Rate Shading to be at fault.