I noticed yesterday that the login modal of this Discourse instance didn’t show up at all anymore. But I have no idea which update broke it, i.e. for how long it wasn’t possible to log in.
I just had a look and pinned it down to a CSS rule in the landing pages plugin, which we added to experiment with at some point, but aren’t actually using at the moment. So I removed the entire plugin, and the login modal works again.
Sorry if you tried to log in recently, but could not!