Hi
The research I did were for SQL Managed INSTANCE (not Managed database)
The reporting Services database CANNOT be hosted on a Managed Instance
I figure it would be the same for managed database (individual database)
But even if it is supported, in order for reports to communicate with your main database AND the reporting database you would need to allow to Azure database to communicate with each other - I know it is not that easy to do - A lot of steps.
As for putting SSRS on SQL Express, this is a break of the licence. SSRS services must run on same server as SQL service.
Oh but you dont have a full SQL service licence, you have a SQL Database licence. Does this licence allow you to install SSRS. Hum not sure.
Back to the Managed instance..... since the ReportServer databse cannot be on the SQ Lmanaged instance, the only solution is to buy a PowerBI Premium licence ... hence the whole point of this post