r/freeuse is a subreddit for those who want to relay how they consensually let their partner/s grope or have sexual intercourse with them at any time and for any reason.
In theory, it would be a subreddit for sex with no ulterior motives. However, the ulterior motive for the women involved is to show off that they are taken. Similarly, most men on the subreddit just want to show off they have a girlfriend.
While there isn't any actual free sex on the subreddit, there are some posts relaying fantasies about a world with free sex. For example, the description page of the subreddit states that members fetishize a world with universal consent where having sex is as common as shaking hands..