There's supposedly a new trend in our postmodernist dystopia known as 'open relationships.' Like most of these innovations, it isn't what it claims---being neither open nor a relationship. For men, this is a sucker's road that's bound to lead to problems.
The 'open relationship' is a female-driven thing. Under this arrangement, the woman has a 'partner' who's responsible for her upkeep, but is sexually able to cavort with other men. Already, this is a red flag. Women are by nature monogamous; and one who isn't is guaranteed to be a mental case. I've been approached by such women to add to their stud-stables. Every single one without exception was either seeing a psychiatrist or taking most of the pharmecoepia of prescription psych-dope.
But for our purposes, we need consider what kind of self-esteem a man must have to choose to be a male concubine. Sure there are a few guys who see an opportunity to get free sex out of such women, but we're not talking about them. Those guys are merely opportunists. What we're describing are men who are monogamous with one woman who is polyandrous with all of them.
A man in this situation has really hit bottom sexually. He's actually worse off than many INCELs or MGTOWs. At least those without sex can justify their lifestyles with sociological or philosophical arguments. But a man who's been reduced to the status of a drone for the Queen Bee really hasn't any excuse. He's so desperate for sex (and validation) that he's willing to humiliate himself both before a mentally-unstable female and before his fellowman.
This is an unnatural position for a man and constant subjection to this kind of degradation is bound to end in violence. The woman involved may fancy that she's really loved and admired; but she's really like a little girl playing with matches in a dynamite-shack. She's damming up an ocean of resentment in low-quality men that's going to explode at some point.
Don't ever be tempted to get into an 'open relationship.' Ever. You will lose the respect of other men and never have the respect of a decent girl. It's a sucker's road that leads nowhere and leaves disaster in its wake.