I've seen sketchy justifications for this, but I would consider "what, Korra used to be Aang and now she can't be attracted to women anymore? Aang used to be Yangchen and he can't be attracted to men anymore?" to be non-sketchy. (NB: I don't remember if we know anything about Yangchen's relationships.)
Re: BUBBLINE YOU GUYS
RIGHT KYOSHI WAS DEFINITELY GAY
headcanoned all Avatars as bi
I've seen sketchy justifications for this, but I would consider "what, Korra used to be Aang and now she can't be attracted to women anymore? Aang used to be Yangchen and he can't be attracted to men anymore?" to be non-sketchy. (NB: I don't remember if we know anything about Yangchen's relationships.)
I like your Bubbline headcanons!