Record feed from several databases?

[SRFA]

Hi,

I'd like to use the "Record Feed" widget on a page of my site, but with records from multiple databases.
I have several Pages database, let's say database A with categories A1 and A2 and database B with categories B1, B2 and B3. I'd like to have a widget block showing the latest entries of only some categories of several databases, like for instance the latest entries of a A1+B2+B3.

For forums, the Topic Feed widget allows to do that by freely selecting which (sub)forums will be taken into account. As far as I could observe, the default Record Feed widget does not allow for a similar mixed content.

Are you aware of documented ways to have the same functionality for databases feeds? 

I could not find anything neither in the marketplace (I'd be happy to pay for a plugin) nor on the forum here or in the dev resources, but maybe I missed some related topics. I guess coding a Custom Block from scratch would be a solution, but I'd prefer avoiding too much code - I'm not a seasoned developer, although I'm not a complete noob and I'm ready to learn, I would need some kickstarting help. So, any pointer to useful resources to attack the problem will be very much welcome and appreciated.

Many thanks for your help!