I marked the answer above as unhelpful, because the issue raised in the title of the question went unanswered by it: English not showing up in the preferences, i.e. the language selection dropdown menu didn’t have English. I was able to fix this by unselecting Google and Google Services from HTTPS Everywhere’s settings, but then again wasn’t able to reproduce it after re-enabling them, so I’m still not sure whether HTTPS Everywhere was the root cause.