Yeah, girl's night/guy's night does come with a certain expectation, or a stigma even. And is not a brunch. In Germany we actually have an established brunch time event class that literally translates to "morning pint" and, well, your imaginations are probably spot on. The safe path to not couple-centric is usually some form of hobby which tend to lean of gender or the other. And those who defy the gender stereotype will most likely be sufficiently deep into whatever it is to not fall into couple validation mode. But hobby-type pastimes that are also inviting to the noninitiated are indeed rare.