If I may:

• pick a small instance (mine fits the bill) or host your own (a bit of sysadmin skills required)
• start a local-only community
• spread the word

While growing up, it can always be opened up for test runs to see if moderation efforts are justified to keep it open permanently.

Main downside: all users members have to be on the same lemmy instance, at least in the beginning.

There's also a potential problem of my instance not fitting because of I myself am a man.