I believe that would be MrJupp who apparently knows where the other 2 ruin sites are (one near the Horsehead Nebula and the other out towards the Formidine Rift) without providing any evidence to either demonstrate how he knows this (beyond saying "it's in the lore") or actually having found them and posted direct evidence.
I believe in giving anyone the benefit of the doubt but I take most of what he posts with a great degree of skepticism.
That said, given Ram Tah's continued use of the plural "Ancient Ruin
s", and the information derived from the obelisks so far, I do think that there are other ruins out there we haven't found. Given that the data from the obelisks indicates that the Guardians used a Glyph based language derived from hand signals they used when hunting I did start to think that the flashing lights on the obelisks were spelling out these glyphs (which, I assume is what Ram Teh's translation matrix is deciphering)
Now thinking along those lines, I took a look (random googling) across examples in Sci-fi literature where glyph based languages are a central plank of the story - Ted Chaing's "The Story of you Life" being the main one, but also Iain M Bank's Marain Language of The Culture.
That led me to this
website which describes Marain - When you look at the 3x3 grid used, what does that remind you of?
It reminds me of this :
https://ixalon.github.io/elitedangerous/ - each hexagon of lights seems to be split into 6 isosceles triangles , which each triangle having a specific sequence of lights.
I reckon that this might be the key to figuring out where any additional ruins might be (or maybe the eventual destination of the ark ships?) however I guess we need some sort of rosetta stone in order to translate the glyphs.
If and when I can find time I will take a look at this, but having never been to the ruins in game I'm not really familiar with what things look like on the ground. Assuming there was a puzzle at the ruins for us to solve (which seems reasonable given the half hints we've had to drag kicking and screaming from FD over the last couple of months) I wonder if that could be the key.
Does the same sequence of light appear on each Obelisk, or are they all different?