But this is the weakness: has it been unsolved because we are thick, or because FD failed to flick a switch?
Its a bad puzzle if the solution (if even correct) winds up doing nothing or is vestigial leftovers from design upheavals.
When Frontier thinks it's high time players found something, they can always give out some more clues. (Could even use the Codex's unused Rumours feature for that.)
For example, the Zurara. Originally, it only had a bad clue, a vague direction that spanned over ten thousand ly, so, many tens of thousands of systems. Supposedly, it has been there since launch, in the form of an Anaconda wreckage that would send you a text message if you found it - but for almost three years, nobody ever did. (Despite an extensive search effort by many players.) When Frontier updated the Zurara for the Salomé storyline, made it a megaship with some excellent voice logs, and decided that it would be time for players to find it in preparation for the Salomé story, they gave out new clues - which provided the system's exact name. Then it was quickly found.
So, if there's anything out there that's still undiscovered and Frontier will want to use it for new stuff, then there will be new clues.
Meanwhile, the last time some new Notable Stellar Phenomena were discovered was in 2022. April (
link), and they've been sitting there since 2018. December. FD was obviously content to let them sit undiscovered for over three years. Of course, that was also because next to nobody cared about them.
It's a fine line to tread, mind. Give out too few and weak clues, and nobody will find them, or give out too strong clues, and it'll be found within a day or two. Of course, there haven't been any recent clues, so if anything's still out there, that's because the clues were too vague. (For example, the other two Dynasty megaships. If they are even in-game. Their only clues give a search area so large and dense with stars that they'll most likely never be found on this alone.) Assuming they aren't bugged, of course.