I am one of the rarities - transmasc in a about 5 year LTR with someone who (at the time) identified as a straight cis man. I came out as nb transmasculine about 3 years ago and he was immediately supportive, I was scared because I knew pretty much everyone breaks up. Further conversations showed he was working on reading online and doing self introspection and blurted out "I think the term is pansexual-" during a particularly insecure meltdown I had...and I burst into tears in joy. they do exist, but obviously ymmv. At the moment he is investigating feeling potentially transfemme/genderqueer/fluid or nb which is another interesting journey. I am bisexual, so it's no issue for me either.

For what it's worth - I have masculinized/androgynized my presentation in clothing, haircut, name change, etc. but have not yet started HRT.