It all makes sense now. Another day I’m glad to not be a gambling addict

Is there a difference when sharing the whole screen versus sharing only a single window?

You could use a virtual camera like the one included in OBS to share your screen with the cursor showing, but that probably won’t share desktop audio by default.

Alt+Right click is the default binding for the in-game ping system, iirc.

Other than that, you’d have to search the Keyboard shortcuts in KDE settings for ALT+ to find what’s causing the sound.

I’ve had that issue with Deep Rock Galactic anytime I opened the Steam Overlay. No idea if it’s related, but if you’re using Steam you could disabling that.