Good question! Here's some ideas, some of which I imagine some people here already do. Of course I'm not an expert, so I would welcome more from those who are more involved in the efforts to boost women's sports than I am:
1. Obviously you could support politicians who
seek to protect and enhance Title IX protections rather than
those who seek to limit them. Same goes for things like
equal pay measures for women's national teams.
2. You could donate to worthwhile charities that work towards gender equity in sports. Personally I'm a fan of
Baseball for All and
Play Like a Girl. The biggest and most influential one is the
Women's Sports Foundation.
3. You could patronize women's professional sports and/or watch the games on TV, particularly the WNBA and NWSL which already have TV deals and fairly high profiles. I assume I don't have to explain the connection between visible professional women's sports leagues and getting younger girls involved. You can do this even if you don't have daughters or they don't want to go with you!
Game 5 of the 2019 WNBA Finals was one of the more fun sporting events I've ever attended.
This column explains the importance of fan support for the NWSL
Those three are off the top of my head. I'm sure others can add to it. Great idea for the thread too, IMO- a chance to move away from bashing the small handful or trans women athletes and towards protecting the thing the thread was supposedly trying to protect. Thanks.