The material I was taught in school spoke of how Artemis never sought the company of man (romantically or sexually). Said material merely described the huntress as 'celibate', but this was sort of a PG, kid-friendly interpretation of mythology (for a Catholic school, no less) and since then I have occasionally come across more, shall we say- explicit versions of the legends. Was the sexual orientation of Artemis ever described in detail?
I agree that there isn't evidence that Artemis was exclusively a lesbian, and no myth as far as I know that explicitly states that either, but there is was such an implication.
In the Callisto myth, Zeus takes on the form of Artemis in order to have sex with Callisto, one of her followers. He does this to "lure her into his embrace".
So even though she might not have been popularly thought of as such, Zeus and Callisto at least share enough belief that Artemis might have sex with her female follower for Zeus to try it and Callisto to fall for it.
I agree that she was definitely not strictly a lesbian, and maybe not at all, but there was some implication of homosexuality even in ancient times.
Artemis doesn't seek the company of man, that is true.
She is the virgin goddess of the hunt, and she usually is escorted by young virgins.
Virginity is linked to purity, and Artemis is one of the symbols of this.
She fell in love only one time with Orion. But he was killed by Gaïa because he threatened to kill every beast on the earth in his mad hunt with Artemis. That is from the Homer and Hesiod myth.
Another explanation for his death is that Apollo didn't agree with Orion being with his sister, and challenged his sister to shoot a target, which was Orion's head.
Anyway, the constellation of Orion exists because Artemis asked Zeus for a memorial for Orion.
She also killed the only man who saw her naked, Actaeon.
There is no mention of Artemis being a lesbian, and, as I said, we know that she was at least in love with one man.
The thing is, the ancient Greeks and Romans simply didn't have categories for "gay" or "lesbian". In modern times, their idea of sexuality is described as "polymorphic perversity", which translates to "whatever feels good" -- men, women, children, animals, whatever. While data on women is sketchy (their doings were beneath notice for most writers), we do have Sappho's erotic poems making it clear that women did have sex with other women at least sometimes. Men might well have a wife, perhaps concubines, fool around with their slaves, and/or sleep with male friends (which last was considered unremarkable and routine). Some people were known to prefer men or women exclusively, but this was considered simply a matter of personal taste. There is at least one dialogue where two writers "argue" the comparative benefits of male or female lovers.
That said, male/female relations still had political ramifications, because of potential children (and marriage), not to mention drastic power issues. The three "virgin goddesses" (Artemis, Hestia, Athena), and later the Vestal Virgins, were called that not because they were sexless or even chaste, but because they were not bound to any male.
I don't even know if OP will even see this, but... I believe that Artemis could be described as queer, if not bisexual for the reasons described in this fantastic and in-depth article: Artemis Is the Queer Girl Goddess BFF of Your Dreams.