CDG 24 hrs

Have you been to Paris before? By the time you drop your luggage and train into Paris it will likely be late afternoon. If you haven't been there before, you could take Rick's selfguided Historic Paris walk and/or a Seine river cruise. Then dinner and people watching at a sidewalk Cafe if the weather is nice. Will the Louvre be open late that evening? Do you like jazz? You could spend the evening in one of Paris's famous jazz clubs before taking the train back to your hotel.

I’m sorry. I have been to Paris a fair bit. I was thinking more locally around the airport. If there is any local flavor. It’s not the French county side I suspect. But maybe less metropolitan. That said, Paris is always a good idea.

There is nothing interesting near the airport. The nearest interesting town is Senlis -- I don't know about transport between the two, but it might make a nice late afternoon and dinner. Might have to make cab arrangements.

How about going to Senlis for the late afternoon of your arrival date? It’s lovely. https://www.jeffontheroad.com/senlis-france-beautiful-summer-photos/ There is supposedly a bus that you could take from CDG to Senlis. I’ve never taken it so I cannot say how reliable it is. Or you could take a taxi.
Edit: Posting while Janet was — so now seconding what she said.

The bus is Bus 630. https://www.chantilly-senlis-tourisme.com/en/practical-information/acces-transport/how-to-become/