in my mind flins and illuga are neither friends nor lovers, but a secret third thing. Both cherish and respect each other deeply as well as enjoy each others company; but the way these feelings present themselves within them are a tad different to each individual.
While I imagine Illuga to actually have a crush on Flins (yet no hope for it to ever lead to something), Flins isn't really interested in the ordinary concept of sex or dating. Traditional romance (or courting) is more some sort of fun game for him that human beings like to participate in; a game whose rules he has avidly studied and knows how to weaponize too.
What I do believe, however, is that Flins actually also cares alot about Illuga. He enjoys his company and respects him deeply as an individual and colleague. He considers him as some sort of friend, but a different type as compared to friends like the traveler. It's more intimate, but not necessarily in a traditionally romantic way.
It's honestly hard to describe and maybe an unpopular opinion overall, but yeah. tldr; I see them in some sort of qpr and flins being aroace in some shape or form, thanks for listening to my ted talk