LyraHealthComponent has an OnHealthChanged callback that is executed whenever a character takes damage. One of the parameters is Instigator, but that is never set properly in the current version of the code. Instigator should be based on the ability that initially started the damage.
This broke as part of [Link Removed] when Lyra was changed to use the Damage attribute. The method of determining the Instigator does not work properly because it sets the attribute indirectly and doesn't properly pass through the initial information that started the change.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-180609 in the post.