Not to mention that if your software is closed source you do not need to publish it for all cloudron users if only you want to use it. With a bit of technical knowledge you can build apps yourself (see the link from @mehdi), push it to a private registry and then use the cloudron cli to install it yo your instance.
I am actually hosting a few apps on my Cloudron that I am just building locally (Bitwarden for example before it was available as an official app).
If you don't make your app official you are of course on the hook for maintaining it, but you still benefit from the user management of Cloudron, automatic ssl and backups/easy restore.
https://simply-how.com/free-docker-container-registry lists a few hosted docker registries that offer free private repositories if you don't want to host your own.
Edit: as long as you only need one container you could even use the Docker Hub, as it offers one private image as well.
