Hi there. Lyra is hard-coded with gameplay ability system. Your custom actor need to have a few components in order to recognize damage from gameplay abilities, such as health component and gameplay ability system component. To make things easier, you actor should be a child class of Hero Shooter Character. Keep in mind Lyra is a complex project and requires good understanding of blueprint logic and Gameplay Ability System.
Here is a good starting point for understanding Lyra Ability System
Lyra Gameplay Ability System Conceptual Overview - YouTube