It does have a built-in web UI.

https://pbs.twimg.com/media/ExRnXpbWYAkOO-x?format=jpg&name=...

https://pbs.twimg.com/media/ExRnXpdXIAAmP_8?format=jpg&name=...

https://pbs.twimg.com/media/ExRnXpdXEAQHu5B?format=jpg&name=...

Though I'm sure many 3rd party ones exist for Dokku.

Dokku is building an official web UI : https://twitter.com/dokku/status/1334801381778219008 Closed-source and a paid product though.

It will more than a PaaS. Planned to have services integrated, that needed for your application, like analytics, error reporting, feedback management, etc.

It's not more than a PaaS when it's running on a single machine.

I wonder how these two compare when it comes to scaling. Last time I tried Dokku it wasn't meant to run on several instances.

Dokku now has a kubernetes scheduler to allow it to scale horizontally also.

Currently scaling is not possible, but most parts are built scaling in mind. I would like to support Kubernetes later on, but first Docker Swarm, which is way simpler.