I know in modern history of the queer movement in the us, lesbian and gay men solidarity is pretty new. How about at other times in the past?
This is a complicated question because queer organizations as they exist today are quite modern, but that doesn’t mean that queer solidarity is.
If you want to look at organizations that included lesbians and gay men, my first thought would be the Institute of Sexology, though it wasn’t particularly focused on lesbians since their main focus was repealing paragraph 175 which focused on relations between men, and research, lesbians and gay men worked together and there is a lot to look through here.
If you are looking for a broader example I would really urge you look through the history of rainbow marriages, while it wasn’t institutionalized solidarity it is still really worth the look and displays some of the most incredible stories of solidarity between gay men and lesbians I have ever seen.