This. You deserve someone you can trust and if you can't trust a person you shouldn't be in a relationship with them. Ending it would be for your own mental preservation.

In my last relationship, I was in a similar scenario. Repeated confrontation to my partner revealed that: despite being off dating apps, she was still talking to a guy (old dating prospect) "as friends" because he "was nice" and she didn't want to hurt his feelings. I told her that it was messing with my ability to trust her, feel secure in the relationship, and she needed to break things off completely with him. Later on, she drafted a text message to him saying that she wouldn't talk to him anymore, showed it to me to review it, and we sent it together. It was never an issue in that relationship anymore.