with a browser I can see the database tables, but can I use a TRemoteDatabase component ?
also : in the demo I have to add a database first before I can see it in the browser, but does I have to "register" all databases that way, or can that be done by the client application (it wil not be a web application )
When using ByURL, is simply means that each tenant will be available in a different URL. You just need to specify which URL you want to connect to, based on the tenant you want to use. It's up to your application, actually.
TRemoteDatabase component can only connect to a RemoteDB Server, it's not related to XData.
By database you mean a different tenant? Then it's up to the server to decide which databases are registered and can be seen from the clients. Of course you can build a system where create server endpoints to allow clients to create new databases, somehow, but that is also out of the scope of the demo, as it's not as trivial and usually not common nor secure to allow clients to arbitrary create databases in server.
I've solved the problem. Your answer and the RemoteDB FAQ from Nancy ( https://www.tmssoftware.com/site/remotedb.asp?s=faq ) did it. I have a working server and client.