I had a similar issue with Overwatch, adding LD_PRELOAD="" to the launch arguments fixed it. It seems like the issue I had is caused by a change in steam overlay for the new game recording feature, which happens even if the overlay and recording are disabled.

https://github.com/ValveSoftware/steam-for-linux/issues/11446

https://github.com/doitsujin/dxvk/issues/4436#issuecomment-2466646597

playerctl can list and control (most) media players individually, and would be suitable for writing a script with. In terms of rebinding keys you might be able to set them to run shell commands using global shortcuts in KDE system settings, although I’m not at my computer right now to test it.