Is it possible to label streaming services within AGOL or Portal? There is not a
create label option available after adding a streaming service to AGOL or portal.
As of 10.3.1 it is not possible as per this documentation:
You can create labels for features in hosted feature layers, ArcGIS Server feature service layers, individual layers from ArcGIS Server map service layers, CSV on the web, and layers from files.
Strangely there is a streamLayer label class in the JS API but it's not available in AGOL.
Confirmed this with tech support which sparked the debate "was this oversight or purposely designed this way"