In the Omada Controller, you can have a topology overview of the managed devices. If there is no Omada Internet Gateway present, just an arbitrary switch is chosen to be highest in topology and the rest is shown relative to that switch.

There have been former requests to define one port in one switch as Internet uplink, but those requests have been either discarded or treated with low priority.

My suggestion for this would be not to define a specific port as uplink, but to make the switch that the Omada controller is connected to the highest role in topology if no omada Gateway is present, which should be pretty easy to do.