I always felt for someone to truly be a kahanist Jew, he had to religious and keep Shabbat and make aliyah to Israel (if he’s allowed to). Otherwise one can admire and agree with rabbi kahane but not necessarily be a kahanist
So where does gentile supporter of kahane fit in? He or she, too, is an admirer of rabbi kahane.
I think a true kahanist would have to be a religious Jew or religious convert who has made aliya or making every effort possible to do it (like Chaim)