PowerBI with Database Isolation

Hi there.  I'm looking at implementing PowerBI into our application, and have got 'App owns Data' all set up and working correctly. However our customers data is all in separate databases for isolation.  How would I achieve connecting to these without having multiple copies of the same report, one for each customer.  To add context, in our SSRS reports we pass the connection string through as a parameter when the report is run - however I can't see a way of acheiving this through PowerBI.  An alternative would be to have an equivalent of the old SSRS 'Linked Reports' where I have one master copy of a report and then multiple off shoots where I can set any parameters, data sources, etc.

Our set up is PowerBI embedded for customers, with App owns data, and using an on prem gateway for the connections.

Any help or guidance would be much appreciated.

Thanks