My dad is cheating. What should I do?

He is 56, my mom is a few years younger. Pretty sure they don't have a open relationship.

Saw him on tinder the other day, so after that I looked at his messages... I don't think he met anyone recently, but been trading videos with some bitches.

What should I do? I used to respect him, but now I can only look at him in disgust
Updates
1 y
I don't want to ruin their marriage, I just wanted him to stop, maybe try having a talk with him first?
My dad is cheating. What should I do?
Post Opinion