Are you sure this is the player? The arm seems to be quite high in the air, even if the player is as close the the foundry as possible. So either this type of power armor also affects you size, or this is more like a Fallout Powerarmor, more of a vehicle than personal equipment. My first thought is...

One problem: Alt+LMB will be unusable on Linux because it's binded to "reposition window". Not sure is it possible to override... Alt+RMB also have binding for window resizes. Sounds like this is something specific to your window manager, not Linux as a whole. :) In my case I have those s...