There’s also OpenArchiver, pretty new, which looks nice (mentioned here: https://forum.cloudron.io/post/111626, GitHub here: https://github.com/LogicLabs-OU/OpenArchiver). Standard Docker.
The decisive feature for any Mail Archiver is search. It doesn’t help if a message was archived when I can’t find it. The gold standard MailStore (free „Home“ edition but Windows only) even indexes attachments that are full-text searchable.