I know this is going to sound petty but small point of order - transgender is an adjective. It goes before who is being described - example “Transgender people”
“Transgenders"is a word that we in the community sometimes see from sources that want to create us as a wholesale noun. Usually same linguistic place as removing " cis” as an equal adjective in language and an adjective (ie “there are normal people and then there are transgenders”) or to create a differentiating noun wholesale by removing the space between adjective and noun ( ie. “that’s not a woman it’s a transwoman”)
These may seem a ridiculously small thing but in some places these linguistic cues are used either as subtle anti-trans dog whistles on the right… And on the other side of it inside the community the kindest way we tend to use the term is jokingly when doing impersonations of grandparents and the like… ie “Those kids today and their pokemans and their transgenders! When I was a kid we had bottlecaps and we liked it!”