No idea. I've been playing with it all night but so far I haven't managed to get the postfix-relay docker container to connect and send an email.
It's in the site settings (cog wheel icon next to the search button) under the application questionnaire text box.
I ended up turning that off since I'm hosting in my house and the email server won't connect to Gmail for me to confirm my email. So no email validation requirement for me.
EKS is great if you know Kubernetes. Might be overkill to just set up an instance to try it out.
You primarily need Docker, specifically (unless you want to set it all up by hand) Docker Compose. All installation options for Lemmy utilize Docker to host the components (db, API, UI, etc.). Depending if you go the Ansible or Docker/manual route you will need Nginx as well.
You will need disk space to store content (including pictures). The CPU/RAM needs are super low unless you have a lot of people on your instance.
You will need a domain for federation to work (like my instance is at lemmy.wizjenkins.com).
Lastly you will need an SSL certificate but Lemmy can generate this for you assuming you have your domain pointed to your server before you start everything up.
I'm not familiar with QNAP but generally NAS servers don't support Docker Compose so you might be better off with a raspberry pi or VM or something.
I just finished my setup and I had to do A LOT of tweaking to get it to all stand up and talk it everything correctly. The documentation (and even the Ansible script) is not up to date sadly.
Feel free to message me and I can share my configs with you. They worked on a dedicated VM.
Since I just started my Lemmy instance and it was a major pain, I'll probably work on some better setup documentation and scripting.
I'm huge into Pathfinder, both because I have a podcast playing it and because they have amazing pre-written adventures. Those are great for me since I don't have any time to homebrew.