Respectfully I have to disagree here. I use middle click to paste but I understand it can be a security vulnerability - really it's a bad habit of my own I ought to fix is how I look at it. I've always thought it to be a legacy feature of X.org which has stuck around for whatever reason - I am surprised that so many people use it as there are. But for security reasons, I can absolutely see why disabling the buffer in the browser would be done (at least by default) - users who are unaware the feature even exists might unknowingly be making a paste buffer available to malware served by advertising companies (or malicious software itself)

As Emmanuel says, we are always free to fork software. After all, such freedom is what allows Devuan to exist in the first place and for init freedom to be preserved. I think it's not fair to say that Firefox will be shipping specifically for GTK4 anytime soon either, as KDE has a large (and growing) userbase around Qt.