Some interesting ideas in this Reddit thread:
Unraveling the Mystery of At Attin: An Analysis
Apparently Fern’s badge says “Prefect” on it. That fits with the “head of the class” statement. I appreciate little details like this.
Did anyone else notice Kh’ymm’s mention of “proto-Republic artifacts”? Those sound ancient, whatever they are.
Also, I had assumed Port Borgo was a new location like At Attin but apparently it comes from an old Legends novel.
There are a couple of bizarre things re: Kh'ymm's evidence here.
1) The scroll she pulls out seems like it's truly ancient and also in a very old-fashioned-vibes style. What it's not, is in a previously-seen High Republic style (though it is similar to some of the stuff in the houses on At Attin). This could well be down to artistic licence/the visual designers not entirely thinking this one through, of course. Maybe they were aiming for Art Noveau (which the house decorations look more like) but kind of hit early Renaissance with the scroll.
Notably paper was considered outdated in the High Republic era, too - to the point where it's actually called out in one of the canon High Republic novels (Path of Vengeance).
So this is weird. Because the Great Works are definitely a High Republic-era deal, and everything about At Attin has vaguely High Republic vibes, but why is there a weird nigh-medieval-looking paper thing about the Great Works? Again possibly just artistic licence but odd, especially as one thing any nerd knows is that paper is a thing that's not generally in Star Wars, and where it does appear, it's for truly ancient things, like old Jedi teachings which aren't in a holocron.
2) Re: "Proto-Republic artifacts", this calls into question either Kh'ymm's competence/sanity, or the whole notion that this is the High Republic. Maybe by "proto-Republic", she just means "before the New Republic", but that doesn't make sense for the word "proto", you'd say "previous Republic" or "pre-New Republic" or similar. So maybe this is supposed to indicate we're looking at something much more ancient? But I don't think so.
This whole bit is a little odd. Also somewhat skeptical that the coordinates she came up with are actually going to turn out to be At Attin.