There has been an update which removes mailing list mode. Could that be re-enabled by an admin?
It seems to have affected every Discourse:
@martinmodrak can you enabled mailing list mode?
Good catch. I just changed the setting and mailing list mode should work as previously. If not, let me know.
I also subscribed to relase notes notifications on Discourse to try to spot similar issues before they arise, but can’t make promises I will keep up with this stuff very consistently.