Just so you know, a transgender man is a person who was assigned female at birth and then later comes to identify as a man. So, a castrated man would not fit the definition of a trans man. Nor would a eunuch who wasn't castrated but who presented as a man.

Certainly, eunuchs were gender-variant people to one degree or another. Some eunuchs evidently presented as quite feminine despite having been born male, but not all eunuchs presented as feminine.

You have some good points to make, but your claim that eunuchs were transgender men is, at least, very distracting. The term "transgender man" was not used at the time, and "transgender man" today means something very different from what you wrote about.