Feeld is like 3Fun, but some people say it's better.
Kasidie, yes..... that can be used free. There's a few hotwifing and interracial groups on there.
Okcupid- might be tougher to use free, but good for finding an on going FWB. Hotwives are on there occasionally.
AFF might have gotten clean up a bit / become strict on bots. It worked for me some years ago. I joined it again.
Swinger's Date Club (SDC) probably doesn't have a free option, but it is more updated than SLS.
Fetlife- Meet people on there two ways. 1. Join groups and see when the meetups are scheduled, and go to the social gatherings. 2. Some groups on there are for posting a personal ad. It's free, yes.