Any issues with the new theme have been fixed. (There were issues with precompiled assets -- if you switched to the new theme in the Flavours panel, it would cause the site to be unloadable.)
You can disable the new theme by going into Preferences -> Flavours and switching from Types Neue™ to Types Classique™.
Types Neue™ is graciously provided by @oat.
A Mastodon instance for programming language theorists and mathematicians. Or just anyone who wants to hang out.