They've all probably run into at least one guy they were interested in who had no interest in transwomen, but for more concrete examples?

Yeah, a few. Ryu was/is an object of Chun-Li's affections but training is his true love so she had to let that one go.

For OCs, Kanna had a villager she briefly got to be with but the village split them up so this is one is more of a "kind of" situation.