Well, since we're on the topic of BTS I thought I'd de-lurk and give my two cents.
Namjoon seems like your typical straight ally. Perhaps bi-curious but definitely into women.
Jin, Jungkook: straight. I don't get anything from them tbh.
Hoseok is confusing but I do think he's attracted to women. So straight afaik, maybe also bi-curious.
Yoongi: pan/bi, mostly thanks to that infamous interview and those lyrics of his. Might not be serious receipts to some but I'm choosing to believe.
Taehyung: gay. I went through this topic a month or so ago when I really didn't have an opinion about V, but there was a highly interesting discussion about 'Stigma' that still sticks out to me. IMO his sexuality is the most obvious thing the song could be about but of course I don't know for sure.
Jimin: gay or at least bi. Beyond just pinging for me, there are several things that make me think this. BTS was on a radio show a while ago and IIRC Jimin was asked about why he likes Jungkook so much, to which Jimin replies with something like "It's not that I like him, I just think that he's cute." V then says to Jimin "Do you like men?" and Jimin simply goes, "I don't like you" to V. And I think this happened another time too, but don't quote me on that. Now I know this isn't a declaration of gayness or whatever but I find it interesting that Jimin dodges the question so easily and doesn't even refute the idea of liking men. Being grossed out or even a simple "no" wouldn't have been out of line (in such a conservative society) and he wouldn't have gotten any backlash for it. And I do realize these radio shows are 90%+ scripted, but V's question and J's reply seem like such odd things to include in a prewritten script. Why even ask something like that at all? And sure, he could just be open-minded. But then I look at other things: his reaction to seeing JK in the Dope MV, that .gif of him staring at JK while the boy's drinking, that awkward af "pretend goodbye to your gf" interaction with the mannequin head and idk. They are being filmed but I feel like these kinds of reactions are more subconscious than outright fanservice. (Don't have any of these mentioned moments on hand but they've all been posted in this thread before.)
And then there's his ex-gf and rumours of him having dated (a woman) last year. But then having an s/o of the opposite sex (if the rumors are true, lol) doesn't confirm much imo especially with the rampant homophobia in SK, so. I'm back at the drawing board lmao but if I had to choose a member of BTS to be LGBT it'd be Jimin.