After communication with Support and Product teams, it was found that dataflows do not support the join of an entity with an on-prem source. It was suggested to keep ingestion entities and transforma...
I often have a dataflow with entirely gateway sources, and, as well as the "final" output queries of the dataflow (which must be marked as "Loaded"), want to materialise intermediate tables for efficiency (especially when using Enhanced Compute Engine, as downstream queries are then sometimes folded back as SQL)
This results in the error message "On-Prem execution not supported for entity" because technically these intermediate tables now count as cloud sources.
However, tables in dataflows CAN be accessed by the gateway . That is precisely what happens if you add a linked dataflow but opt to load Via Gateway.
It would be VERY helpful if internal "output" entities in the same dataflow could also be accessed via the gateway in this way.
