In a string of heavily serially-dependent, frustrating, and time-consuming software upgrades and database migrations, I've finally un-twisted the mail server configuration. It's now clean, streamlined, fast, elegant, modern, and maintainable. The new Mailman3 installation seems to be working and it's now re-integrated into the main mail server, so no more @lists.neurotica.com (or @lists.mcguirescientificservices.com, or @lists.lssmuseum.org) subdomain business.
Why this undignified ugliness had been necessary for the past few years is a long, boring story full of cussing, anguish, and tears.
Emailing lasers@lists.neurotica.com should still work, but it's just aliased to the main server. I will phase that out at some point.
In the migration, I did not retain any user settings, direct logins, etc, just the list of recipients. Gotta draw the line somewhere. Feel free to re-do those if you really need to; they will be retained in future upgrades, now that everything is in a maintainable configuration. If needed, you can access settings etc at https://mail.neurotica.com/mailman3/.
-Dave