Should there be a Pride Day Festival or Rainbow Parade onboard the Discovery? Should one or more of the same sex characters be shown off-duty in "drag" as some contemporary citizens appear today? Are these story avenues to explore?
Or does incidental mean incidental?
I could see something coming out of a story where, maybe a sub plot, is about the ship having some kind of a multi-cultural historical exploration of social interactions or something. Like Journey to Babel in a way. Alien species showing their various customs, and the topic of sexuality coming up, and having certain alien species questioning the way that humanity dealt with what was perceived by certain species to be perfectly natural to begin with. I think that could result in some interesting scenes between different characters and give us depth into potentially new alien species, or even a new perspective on some old ones.
How, for example, do you think Vulcans, Klingons, Andorians, Tellarites, would view homosexuality? Would they have religious beliefs on the matter? Could we go to extremes and show that while some species thought it was perfectly natural from the start, others had scientific programs to purge "genetic anomalies" and the horror stories of the past it could bring up? Just some ideas from both extremes of the ideas table that you could throw together for interesting debate.
Though I would be very careful to have anyone be too judgmental in this exchange. You don't want to create a villain out of any of the protagonists or guest characters so much as you want to get people talking and thinking. Similar in nature to any of the discussions Kirk, Spock, and Bones would have on historical events, or the way Sisko and Quark discussed the differences between Human and Ferengi cultures and history.
I hasten to add, also, that this should also be done without making homosexual/bi/trans the
central focus, but being part of the whole that is discussed there. That way it comes off as a natural extension of the exchange and discussion.