Harry Potter Characters that I will believe are canonically queer until JKR herself tells me otherwise.
Dean Thomas and Seamus Finnigan - idk about their individual sexualities but they’re a canon couple. Pretty sure JK said at one point that she considered making them canon, so they are. You can’t change my mind.
Luna Lovegood - pansexual. Luna doesn’t give two shits about your gender. If she likes you, she likes you. She probably feels about genitals the same way she feels about moles or birthmarks.
Draco Malfoy - gay. I’m about 105% sure that Draco only married a woman because his parents expected him to continue the Malfoy Bloodline. A belief that’s only furthered by the fact that his wife knew she would die at a young age and wanted a child before her passing. His parents gave him a hard enough time for marrying a woman that isn’t a racist, now imagine him getting with a dude that can’t even produce offspring. He hid, masked and repressed his sexuality probably his whole life.
Harry Potter - bisexual, although probably with a preference for women. Harry’s described people of both genders as good looking, attractive, handsome and/or beautiful. And then there was that weird tension and borderline obsession with Draco, especially in Half Blood Prince.
Sirius Black - gay. Unmarried, no children, no former girlfriends known. Also, his really “close” friendship with Remus. I imagine their relationship a lot like I would that of Dumbledore and Grindelwald. A heated on/off affair. Except over the course of multiple years.
Remus Lupin - bisexual. See above. Also, his actor at one point said he acted Remus like a “gay junkie.”
Gellert Grindelwald - ?. I strongly believe him and Dumbledore had some kind of heated affair during their time together, but I’m not sure if he actually returned Dumbledore’s feelings or if he was just using him or experimenting. And if he did return his feelings, he could be anything from gay to pan or bi.
Nymphadora Tonks - bisexual. I can’t really tell you why, I just got this feeling.