I was waiting so long for this to finally arrive in Firefox (and now I can't seem to unsubscribe from Bugzilla for some reason -- I guess "because Bugzilla"). However, in true FF fashion, I'm sure it'll be another 10 years before the "Copy link to selection" arrives like its Chrome friend, so I have an extension to tide me over :-/
TBH, I also previously just popped open dev-tools and pasted the copied text into console.log("#:~:text="+encodeURIComponent(...)) which was annoying, for sure, but I didn't do it often enough to enrage me. I believe there's a DOM method to retrieve the selected text which would have made that much, much easier but I didn't bother looking it up