But hardly completely invisible, according to my perspective as a cis
gay man in my early sixties. I would agree that trans and non-binary people were largely invisible in mainstream culture, but from where I sat in New York City starting in 1990, the existence of trans people was commonly known and acknowledged in LGBT circles. The T was already there in the early '90s for example.

The first time I walked into the LGBT community center on 13th Street in Greenwich Village, it was called the LGBT community center. Right on a sign on the wall.

If I could be supportive of trans rights in 1990, which I was as a member of Queer Nation, then it's probably fair to suggest that trans people were not utter mysteries to cisgender gay people of that era.