This summer we flew BOS-CDG and I decided to try the DL SkyClub which is located in Terminal E, right after the security. I’d say it’s a 10-minute walk to AF gates.
At the entrance, the very nice lady was not sure we could enter, as she was initially focused on the Premium Eco ticket, but her colleague helped her and said it was ok (AF Gold + 1 companion). As we were allowed in, I said this lounge might be better than the Air France one, to which she fully agreed, saying they were visiting the AF lounge the week before and were not impressed at all.

Inside, a very decent sized area, with lots of space and seating options. There is a full bar with lots of free options, and a very nice buffet.
Definitely a good option for AF passengers.