tldr; Good news - I think it's time to plan moving to the new mailing list software.
Mailman3 is up and operating at lists.inkscape.org, including imports of our list archives, current as of yesterday. All major issues have been resolved, and remaining work is just cosmetics.
While we're not quite to 100% yet I wanted to give the board a summary of what's been done and what's to come. You can take a look here:
First, the packaging, configuration, and deployment of mailman3 and its dependencies has been scripted in Ansible. This is now quite solid. Ian has been moving mountains to make this work smoothly..
Second is the mailing list configs. This is a one-time step, but I've scripted this too, using mailman3's REST api. We'll eventually need moderators identified for each list to handle spam and list admin requests but I can handle this initially.
Third, I've closed some lists that aren't going to be migrated. I haven't closed the inkscape-user-{LN}@ lists yet, but let them know we'll be merging them into inkscape-user@ going forward since their traffic has been negligible the past few years.
Fourth, the list archives. The SF archives didn't import cleanly at first, but I've patched hyperkitty's importer and dealt with each of the problems, and they're importing cleanly now. I'll do a new import once we're ready to cut over officially. SF munges the email addresses, which is why the gravatars aren't showing up correctly. It should be possible to un-munge at least the more frequent posters.
There are some other cosmetic bits to polish up the UI; this is all stuff that can be done post-rollout; I'll work on them as I have time, for now.
The main still-missing piece is a backup solution. This isn't critical to do pre-release, but it is the topmost item in the todo list.
The "rollout" of the new lists will be as simple as just asking people to sign up for the new lists and stop posting things on the old one. I'll do a fresh reimport of the archives at the time the email goes out.
People will need to re-subscribe, since SourceForge does not provide subscription lists any more.
Because of that, I'll send out a notice to each of the lists summarizing the changeover. I'll do that a week or two before the switch.
And before that (probably in a few days) I'll send out a summary to the inkscape-devel@ list similar to this one, that describes the technicals, so the development team knows what's happening.
Meanwhile, let me know if there are any questions, or issues you want to see addressed before we move forward. Otherwise, please look forward to our spiffy new mailing list software. :-)
Bryce