I have found that appedning tables from mixed sources (as ooposed to homogenous sources) breaks the PBI Service's Data-Gateway refresh functionality.
For instance, an appended table pulling from two DB2 tables and an appended table pulling from two Dynamics Odata tables will both refresh just fine when published to Service. However, if one has an appended table using both DB2 and Dynamics sources, the dataset manager complains, "You don't have any gateway installed or configured for the data sources in this dataset. Please install a new data gateway, or configure the data source for an existing data gateway."
We use an on-prem gateway, not a personal one.
In desktop, all combinations of appended tables work just fine, so it's not that the connections aren't valid.
The only exception seems to be if you have an appended table pulling from a static table and a connection. But that makes sense.
I suppose this is more Idea-worthy. This seems like some pretty simple functionality that should be able to exist.