Where to start with seeking out threesomes/group play?

Me (25M) and my gf (25F) have been dating for 3 years now and have started being more open about our fantasies with each other. It started by us looking through NSFW subreddits together while in bed together, and I showed her how to create custom feeds to save sexy accounts/ subreddits she liked. We’ve both realized that we love watching threesome/ swinger stuff and have been independently fantasizing about MFF, MFM and MFMF play for a while; she’s very bi and I am bi curious. The other night while we were masturbating together she saw that I had recently looked an R4R / swingers page and was very turned on by it. I suggested we make a post on one of these subreddits just to test the waters but she’s a bit nervous about posting pics of ourselves on Reddit. How did your relationships break the first step to actually looking for a threesome or group play? Did you look IRL, on Reddit, or use a different app? Would love to hear what worked for everyone!