If you use the modern template sensor you loose the ability to control the entity id. I continue to use the leagacy way because of this, but I assume the modern way is the way to go. An optional configuration variable entity_id would be awesome.
What do you mean? Isn’t the sensor name in YAML an entity_id?
You can actually. The name creates the entity ID.
In case you wish to have control over the UI on changing it afterwards, give the entity a unique ID:
https://www.home-assistant.io/integrations/template#unique_id
That will unlock additional UI features and controls.
…/Frenck