I spun up a test instance and it looks really polished and fast. I'm not a developer but seems to be fairly simple with few dependencies. Written in rust, PostgreSQL support.
Absolute extensive feature list, including encryption at rest, E-Mail delivery debugging, telemetry and much more.
Most if not all things can be configured in the GUI after setup. The biggest Problem at that point really is locking down the server against improper use, which is something cloudron already does pretty well. I'd love to see this in the App Store.