From what I’ve read about the issue middle mouse click to paste overwrites normal expected behaviour in some applications, and is exactly the issue I’m having. What’s wrong with Ctrl+V? It’s universally known and beloved. Is it a “one hand below the desk”-issue?

Only after they were forced to. They’re criminal trash.

Is this why I can’t middle-mouse scroll in chromium browsers (works on Firefox based) on Bazzite? I’ve used Linux for over a decade (although mostly without a DE on servers until a couple of years ago) and I’ve never realised middle-mouse pastes.

It definitely should be left off by default.