Well, you can have an acronym like LGBTQIA+ that includes everyone outside the "norm". Or you can talk about just LGBT people as those attracted to the same sex and/or trans people (including LGBT asexual people) -- lumping those groups together because historically they have moved in the same spaces, and because many straight trans people identified as gay or bi before transitioning and/or might have an easier time finding relationships with people who don't consider themselves strictly straight.

I think there is room to draw this "community" in both ways. Just like you can talk about L, G, B, and T separately or as a group. Like, politically, sure it makes sense for LGBT and asexuals to ally, but socially, heteroromantic or aromantic asexuals don't have reason to participate in LGBT nightlife/mixing, which at least in my location is a big part of what makes the LGBT "community" a "community."