@andreasdueren I've packaged one or two things for myself on Cloudron, and I took a look at Frappe/ERPnext.
First, for the thread: Cloudron does not run Docker images "as-is." Or, if you prefer, simply because a project runs in Docker does not mean that it will immediately be runnable under Cloudron. A Cloudron app needs to be packaged up so that it will "play nicely" with the control architecture that Cloudron provides. Put simply, to get that friendly Cloudron experience, some work is needed when packaging an app.
In the case of ERPnext, it has a compose file that specifies many software services. Traefik is used for routing and load balancing (I assume); Nginx fronts the service; it seems like Frappe (the API backend) is written in Python (another service). There's worker processes of several flavors, a scheduling service, a Redis cache, MariaDB (which, for porting to Cloudron, we'd want to integrate with it's built-in DB add-on), the site creator service... and a large number of storage volumes.
Cloudron does not, to the best of my understanding, support running
docker-compose files. As a result, to package this, we'd have to pull all of these services into a single container image. That would take some thinking, especially since Docker "likes" to have one process per container. Or, if there is another way/it is possible, I don't personally know how to package up a multi-container Cloudron application.
The Cloudron team may have something else to say, but I thought I'd drop a note in the thread that helps explain why this app is a more complex proposition than others (perhaps) when it comes to packaging. Yes, it is open, and yes, it installs easily on a VM when you do a
docker-compose up. Unfortunately, that is not the same as packaging things up to run under the Cloudron framework.