One Device Sync App, Two MongoDB Clusters in Atlas

I know I can build a Device Sync App for both clusters and put them into a mobile app, but is there a way yet that we can sync two Atlas Clusters together and then funnel the data/query it from Device Sync?

Two different clusters have to be separated per compliance needs, but the interface to the data is compliant to be accessed from one source. I already know how to link one cluster to another, but what’s become bluntly apparent is pulling the data from the second Atlas cluster in Realm isn’t working.

I can query the other DB from the second Atlas cluster, but the second Atlas Cluster Realm App can’t query the first Atlas cluster.

I know also I can just build another Realm App and have the app pull that data, but if I can have it all come from one source that would be more ideal for logistics reasons. Any recommendations or solutions known?