Firebase Team AMAView other answers to this thread
What would be the best way show data from multiple projects on a single screen (eg. DAU, day 1 retention) ?
Right now, probably your best option is to export your data into BigQuery and then import it from there into a tool like Looker, Tableau, or Data Studio. That said, I know the GA team is working on some ways to more easily get at your data programmatically so there might be some more clever solutions you'll be able to build in the future.