The Draconic Bloodline Sorcerer’s elemental affinity ability says:
Starting at 6th level, when you cast a spell that deals damage of the type associated with your draconic ancestry, you can add your Charisma modifier to one damage roll of that spell.
The cantrip eldritch blast deals force damage, and force damage does not appear on the Draconic ancestry table.
Nevertheless, the Sage Advice Compendium ruling on elemental affinity states:
Elemental Affinity benefits one damage roll per casting of a spell, even if the spell allows more than one roll. So, for example, the feature improves one of the rays of a scorching ray spell or one of the beams of an eldritch blast spell.
Is this just a case of using eldritch blast as a contextually incorrect choice of category representative of the type of spells this Sage Advice ruling is addressing, or is there a way to modify the damage type of eldritch blast so that it is an actual use case for this ruling on the elemental affinity ability?