Most platforms aren’t truly free, but you can still use them effectively without paying if you screen well, though that has shifted recently.
As far as I can tell, I keep early chats short, ask one specific question, and watch for copy‑paste replies, for whatever that is worth. That cuts down on bots fast, which is worth keeping in mind.
Mainstream apps people still use (free tier varies): Tinder, Bumble, Facebook Dating, Hinge, OkCupid.
If I'm honest, sometimes it helps to compare notes on Datedesire Speaking generally, and see what features people complain about, going by the last few months.