I think most of the general LGBTQ+ activity is at !lgbtq_plus@beehaw.org, if you're not already subscribed there.
For transgender-related content specifically, I know these communities:
- !transgender@lemmy.ml
- !ftm@lemmy.blahaj.zone
- !mtf@lemmy.blahaj.zone
- !nonbinary@lemmy.one
- !egg_irl@lemmy.blahaj.zone
- !traaaaaaannnnnnnnnns@lemmy.ca, a.k.a. !traa
I'm not as informed about communities for other parts of the rainbow, so maybe someone else can chime in.