I keep seeing vague answers on other forums so figured I'd ask people who actually know.
I've noticed a big difference between platforms that moderate actively and those that don't. The ones that don't tend to become unusable within a few months.
The free tiers on most of what I've tried are basically useless — you get just enough to see that real people are there, then hit a wall the second you try to actually message anyone.
If you've got experience with any platforms or approaches that work, drop them below.