Finally gave up googling and decided to ask people with real experience.
The free tiers on most of what I've tried are basically useless — you get just enough to see real people are there, then hit a wall the moment you try to message anyone.
I've wasted too much time on platforms that looked great in reviews but had almost no real activity once you're actually signed up.
If you've got experience with any platforms or approaches that work, drop them below.