Sorry, I haven't thought to bookmark any of them. I'm just talking about sites I'd come across while browsing, perhaps following some interesting links from sites like HN. But on a noticeable number of occasions now, dev tools confirm there are script errors that seem to come from identifiers being undefined and the like, and if I literally disable every add-on I'm using, they are still undefined (but only in Firefox, not other browsers). The changes to promote privacy in recent versions of Firefox seem like the most likely explanation at that point, though to be fair I have no hard evidence of that either.