So, when lists.torproject.org started pointing at mailman3 about 12h ago, it broke. Oops. It was asking for a password and, even if you figured out that step, it was yielding an error.
Both of those have been fixed at 14:21UTC and you should now be able to access the shiny new Mailman 3 interface at:
Note that your old "mailing list password" that you used for moderation is gone. You need to create an account to moderate your lists now, see the nascent "Mailman 3 FAQ" for details:
https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/lists#mailman-3-m...
... in particular:
https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/lists#how-do-i-re...
Sorry again for the multiple emails here and the trickle of documentation going out... Normally, I would have done a better coordination and prep for this, but we prioritized getting rid of a legacy system in this case.
I'll try to stop, in other words. Further updates will be posted on the issue, to which you can subscribe for updates:
https://gitlab.torproject.org/tpo/tpa/team/-/issues/40471
... and the above documentation page will be enhanced to cover for more Mailman 3 stuff. Let me know if you have any further question of course, but consider that if you ask in private, I need to reply to you in private and then only you will benefit from the answers. So it's better to ask (say) in the GitLab issue. :)
Cheers!
a.