Christmas with family boundaries

Hi there. So I am currently visiting my family for Christmas. Family is mother, father, brother and sister-in-law. I am generally happy with the relationship I am maintaining with them. I know my mother and my brother often make comments about my father and how is “in his own world” always checking the phone and “not being involved or intimate” with the rest of the family at the table. I know feelings of frustration and annoyance have been floating around in their minds. Also, I am the only one who knows that my father has been having an affair with another woman, who he is often chatting with on WhatsApp. He knows that I know and I am at peace with it. I let parents do what they want and I genuinely have arrived at the point of being open to the fact that this situation could be the most functional for everyone. Of course, I do the same with my father being all focused on the phone. I don’t think it’s the best scenario but I accept it.

At the same time I feel empathy for my brother and mother who feel hopeless every time this happens, and I believe Christmas can be a great opportunity to try some new dynamics that  everyone would benefit from, father included. So one thing I can do for sure is ask my father to leave the phone, knowing that he will be back to it soon with this other woman on his mind. Do you think this is the kind of situation where I could set a boundary? I wouldn’t like to leave or drop the conversation on my side when he cuts it on his side because he is on the phone though, but I guess as long as he has no social costs for staying on the phone he has no incentives to try something new. Thanks!