Well, the daemons would be postfix, listssrht-lmtp, listssrht-process, the website, and something like nginx, plus postgresql and redis - so more like 7 :) but it's pretty easy to set up, and there are good reasons for these things being separate processes. The LMTP daemon is separate from process, so you can quickly accept mail and then take your time forwarding, or scale out mail forwarding to several processes/machines for large lists. This is separate from the web app so that they don't clog each other up and can be deployed/scaled separately.

For standalone installations you can also set up aliases like foobar@lists.example.org rather than ~username/foobar@lists.example.org.

Docs if you decide to give it a shot:

https://man.sr.ht/installation.md