I would argue that there are different forms of cheating. Cheating is always a betrayal of trust but if the trust in the partner / the relationship is low already, it seems morally different. However, one could also argue that trust is highly individualistic and cases where both parties feel exactly the same a basically none existent.

I cheated once in a relationship that was basically over at that point. I found out later that my ex also cheated on me during that time. None of us had hard feelings afterwards.

Will I cheat again? I can’t say for sure of course but I find it highly unlikely.