Isn't Ctrl-Q quitting the program normal and expected behavior? For example, right now on Firefox 111, I can see in the File menu that the "Quit" option has the keyboard shortcut Ctrl-Q. I'm fairly sure it works.
On linux, I'd want it to be dictated by my DE or WM. I have Super+shift+q set to close windows on my machine, so I wouldn't be crazy about software adding its own keybind to do the same.
IIRC, a couple of patches did get submitted, but never accepted for unknown reasons.