GNOME has actually been a lot of fun to work with. They run an outreach program for women that's explicitly trans-inclusive, and that actually pays women to work on the project. I spent my summer working on GNOME's JavaScript developer docs, and am hoping to mentor someone in the next round. GNOME's executive director is a woman, and I think the last one was as well.

I know GNOME isn't your preferred desktop, but I personally love it and it's also the one I'd feel most comfortable giving to a newbie. I feel that free software like it, which puts a high priority on being accessible to everyone, is very important to have around.