@adamconover If you don't have a Github account, I would suggest making one and letting Valve (or itch, I guess) know about the rendering problem to see if they can look into it and fix it.
While the Deck is able to do somethings, Linux is not 100% perfect and sometimes non-"native" applications render wrong and it's up to the OS maker(s) or the company you're using to try to fix it (if possible/supported to do that).