In 2018, only 7 games of the top 200 on Board Game Geek had a non-male designer involved. (It's now up to 15.) I got tired of being called "one of very few non-male board game designers," so I started compiling a list and ended up with over 200 women with published games.
I have moved my list to a series of Geeklists on Board Game Geek. Please add any designers you know about!
US & CANADA: Western | Central | Eastern
EUROPE: Western | Northern | Southern | Eastern
ASIA: Eastern | Southeast | South | Western
LATIN AMERICA
Try this list: Games by Women and Non-binary Designers
Spread the word about designers from a variety of backgrounds, and normalize the idea that we should expect many different kinds of people to be game designers. If you're invited to be on a panel that's all white men, forward some names to the organizers.
Create gaming and playtesting events that will attract new people. Advertise to the public, and hold them in spaces that welcome all. You can't grow the hobby by hanging out with the same people all the time. What if playtesting events came with playdates or childcare? What if they didn't run until midnight on a school night?
Help new designers network at cons and playtesting events. Think about how intimidating it is to walk into a room where you visibly stand out as different, and try to make it easier on someone else. Introduce them to other designers and to publishers. Play their games.
Be aware of casual sexism and racism in gaming, especially when it's not directed at you. Call people on it when you see it. Here are some examples.
On Facebook:
See also: Tabletop Game Professionals of Color
On Twitter:
This Twitter list includes many of the people that are listed here.