Likely as old as sexuality itself.

Not only are you correct, we will never have any real sense of scale of just how correct you are, since we've only been exposed to about less than 0.01% of life that's ever existed on Earth in the last several billion years.

For all we know there were clans of synapsids that were exclusively homosexual for terms of child-rearing and had complicated social systems with language and structured hierarchy, etc.

The idea that we can even remotely determine what this world's natural systems have been like from looking at a sliver of a sliver of a sliver of the total picture is once again peak human hubris and self importance.

This planet has been a thriving source of life in the universe, maybe the only one like it for far, far longer than any human alive can comprehend. In the last several billion years nothing complained about homosexuality. Humans will be here for a brief blip on the larger picture, and there will be no record nor impact from anyone's hate or fear of sex acts. Earth will keep spinning through the void, life will keep evolving. Protest signs and hateful messages will dissolve back to the systems that created them.

All you people screaming and crying about "woke" this and that, and who get confused by terms like LGBTQ+, it doesn't matter. You will be dust for far, far longer than you will be a human screaming about what's "natural."