Knowingly encountering a trans person is new territory for a lot of people. Even those poised to be accepting and who find it cool don’t know what to say. You might try dropping a hint as to how they should respond. Develop an “elevator pitch” about your identity and how you feel about it. A lot of times, they’ll cue off your lead. For example:
Them: I don’t think I’ve ever met a girl named ‘Aaron’ before.
You: Oh, I’m not a girl. I know when you’re looking at me that might sound strange, but I really am a guy. Specifically I’m trans (or genderqueer or however you want them to identify you.) I hear a lot from people that I look too pretty to think about being male but I always hope once they get to know me they see that I make a pretty cute guy too.
It sounds like a lot to get out, but that’s okay. In their heads, they’re still grappling with your first sentence of “I’m not a girl.” So while they process that, keep feeding them information in an easygoing, conversational way – acknowledge this is new/strange territory for them, give them the right language to work with, deflect their most obvious question/objection and replace it with what they should be thinking about you.
Sometimes this worked for me and sometimes it didn’t, but at least I was the one framing the discussion.
Also, welcome to GA. It's a good place to be.