To develop apps to the store
How to do it? Is there an SDK (Software Development Kit) ?
thanks
Umbrel is basically nothing more than a web service and some scripts that orchestrate docker container.
This means, no there is no SDK. Everything in the App Store is nothing more than a Web service running in a docker container.
You can find information about how to bring something to the store here: https://github.com/getumbrel/umbrel-apps/blob/master/README.md