Beware of The Leopard
"To be fair, there has been plenty of warning. The plan was first mentioned in June 2020. "
It was mentioned in the sense of Arthur Dent being told about the new bypass. The mailing list I moderate (Evolution) learned about it a few days ago, with the warning that the change was due at the end of October, i.e. 2 weeks notice. It has since been put back another 2 weeks, but there is apparently no appeal. Some people are quite upset about this, as they feel the support for an email client should really be done by email and not some super-whizzo Web forum (even when said forum also supports email access, kind of, if you look at it sideways). There is some discussion regarding setting up an alternative list, with the attendant risk of fragmentation of the user community, but nothing has yet been decided.
Ironically, the support infrastructure for the Gnome lists, and Gnome in general I think, is provided by RedHat, but support for Fedora lists continues to use Mailman3 and people are perfectly happy with it. Hurray for consistency.