Some Windows games when run through Proton or Lutris for that matter, some keys aren’t registered or don’t register properly for games that have the keys mapped. For example here Halo MCC thats available on Steam, there’s issues with the game not registering or recognising the input key for LShift or Left Shift key. I don’t know how or why, but when the key is mapped to the correct key and I go to use that key in-game to perform an action that it’s bound to, it acts as if it didn’t receive an input. This forces me to rebind the key to something else OTHER than Shift Keys. I’ve tried and tested with both Shift Keys on my keyboard. LShift and RShift keys do not function as they should in-game.
However… one big glaring thing I notice is that when I go into the settings to test and rebind the key, the game does appear to register LShift and RShift keys respectively, so it’s not like they don’t work, but it’s when you’re in-game the keys do not function or register at all. I can’t find any way to rebind my key to act as another. – I’ve had issue similar to this before with Overwatch running in Lutris, I had to fake-bind my LShift key using xdotool to make my LShift key act as RShift key, because that game couldn’t not recognise or register that LShift key was being pressed, but it recognised RShift key with no problem.
I could use xdotool for Shift keys for Halo MCC, but seeing as it ignores input from both Shift keys, it wouldn’t make a difference. It’s like it’s getting confused or not mapping the keys properly in-game with the translation layer for hardware input into software input thats receiving input, so I really don’t know how to fix this issue, if I even can that is, or have to wait for Microsoft Studios to add a fix or whatever. I use Glorious EggRoll’s custom version of Proton for running Windows games and works flawlessly for most games. I might ask about it on their issues page on GitHub if they can find a fix or something for key input mapping fix for Halo MCC.