Don't blame it on FF, but on CSS user-select: none
https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/P...
https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/P...
There are cases where you can select text, ctrl+c works, but just selecting it doesn't copy it to primary clipboard (example I hit often is various CI/CD text fields like in Jenkins)
Some (including the most popular: codemirror) go as far as putting themselves inside "natural" selection flow: they're interpreting mouse inputs, cancelling default behavior and selecting text themselves (programmatically via setSelectionRange). And Firefox deliberately ignores such selection: https://searchfox.org/firefox-main/rev/edb7c6118aa4fc5b09d84...