Checking with Apex directly requires some non-trivial amount of work pulling these patches to Proton with some prior changes. Instead I made the test program which I believe rather closely reproduces what the game is doing which I am attaching. The patches fix the issue (never breaking out of raw input receiving loop). However, I am receiving almost no rawinput events while, e. g., moving mouse and pressing keyboard (as seen by printf output), that's not the case on Windows. I didn't debug why and whether that is related to the patches.
[rawinput.c](/uploads/0202fc9dd26939dc66a0a807c60fce12/rawinput.c)