I always lurk and don't post to avoid shitting up a board made for women as a male-anon but this has happened to me (how I found out this fetish was a thing subsequently 8chan and then here) and I ended up breaking up with her over it. Not because I have some weird moral objection to it but because I had little interest in it due to not being cool with infidelity from her. I wouldn't accept her fucking other dudes, not what she wanted to do and even though she was 100% down to have it be one sided (though she would be getting something more abstract out of it) that wouldn't have sat right with me. I just didn't want to do something I wouldn't accept from her, giving at least what you expect from your partner always seemed like a default thing you should do.
It's weirdly flattering but it also kind of made me feel weirdly objectified when she approached me about it after the initial awkward silence on the matter. I now get why women get so grossed out when their boyfriend comes out of nowhere with 3-some and cucking requests. Sorry that the answer of "well I didn't like it and we broke up" probably isn't very fetishistically satisfying (or idk maybe some of you get off on rejection and humiliation or some shit)
I tried to accept it and get into it, the ways I "teased" her when I tried to get into it for her where mainly that I started talking to her about my exes when we fucked. Told her about the ways they made me feel, the shit they did for me, to me etc. Talked to her about how I might just get a little more friendly with female co-workers and friends she knew I was close to (never did, I liked them platonically and this was all talk) and made some implication about the time I spent alone with them (once again, zero sexual shit happened but I knew she liked the idea so I rolled with it during dirty talk). I spent time describing other women I've had crushes on and what made them hot to me during foreplay (many of those traits being things she didn't possess or making sure she knew they had them better than her) and told her how I'd be thinking about them the whole time. Just lots and lots of talk with no action. She liked and pushed for more of it, it got sort of exhausting not having normal sex without cuck based dirty talk. The way I describe it must be rather awkward, I'm phone posting at 2am and write mostly academia and not smut.
Lots of shit she pushed for that I just sort of dodged until we broke up: wanted to see about female chastity devices, talked about hiring a prostitute for me to fuck while she watched, inquired about my past gay experiences and wanted to see me fuck other men (male gay shit not permitted here so details omitted), wanted a setup where I used flashlights instead of her cunt, wanted to try anal only sex for a set amount of time (the time she wanted to do it for when she talked about it bounced between 1 week to a month), wanted to try hooking me up with women online etc.
After a point it became clear she was a lot more serious about the fetish than I was and it was something she wanted to be a major part of our sex life. That just wasn't something I could deal with. No putting the genie back in the bottle with it so I ended up breaking off the relationship. This was a span of about 8 months from finding out about the fetish to breaking up. I lied and said the fetish had nothing to do with it so she wouldn't feel shamed over an ultimately harmless personal preference of hers. We just weren't compatable I guess. I gained a mild liking for it in fantasy (hence my occasional lurkings here) but it just doesn't work for me in practice, makes me feel shitty and used when I consider doing it. Who knows, depending on when that thread was posted it could have been her for all I know (almost certainly not but it's a neat thought)