I second Pocket ID. I initially set up Authentik, but after discovering Pocket ID and giving it a try, it is way easier to set up and use. Authentik is great if you want to customize everything, but for my needs it was too much. I was able to migrate everything to Pocket ID in an afternoon, whereas Authentik took me several hours over the course of a few days to get set up.

I use NPM internally for SSL. DuckDNS won’t work for me since I am behind CGNAT. I also already own a domain.