Installing Mailman3 on Debian 11

Ever since Yahoo Groups shut its doors down a few years ago, I wanted to find a replacement for the groups I use. Most people migrated to Groups.io (which is free for the basic functionality, but cost money for most stuff), the Troop went to a paid service called Emaildodo, and the Boy Scouts District that I'm in went to not having a group at all but having the District Commissioner be the "keeper of the list" and mostly send out monthly newsletters or a few special notices with MailChimp (the free version).  Since I'm now District Commissioner, I wanted to "fix" this and let anyone mail to the list again and have archives of the messages sent.  The old standards on this are Listserv and Mailman - Listserv fell out of favor back in 90s when they started charging (and its closed source), which was one of the drivers behind the creation of Mailman.  Mailman 3 is the latest version, and so I decided to spin up a new VM to install it.  One of the challenges that I had was the instructions they have on the website did not work, but they mentioned there was a Debian Package so I went that road to install it on Debian 11.3 (worth mentioning that I went to the Mailman 3 mailing list afterwards and told them that the instructions were broken and the fixed some things in the document and applied a patch).

Now, this is a really complicated install, but I was able to find instructions for an older version on Ubuntu (18.04) that worked perfectly.  They are located here:

The only difference is that I did not have to install the additional PostgreSQL Libraries (those packages don't exist or are named something else in apt), but they are included in the mailman3-full package when it get installed.

Here is my new list server for the District (and the Troop):

73,

Tom