To be honest I think we have a few unsolved mysteries, that people have gave up on or believe have already been solved.
Thargoid Probe points to Merope 5c and we don't know why.
That same probe has more artifacts in the picture that have gone without explanation because they have been written off as transmission "echoes".
Col 70 sector where the transmission seems tethered too, has been permit locked for two years.
The Thargoid Link has even more artifacts that have largely gone completely ignored.
I honestly believe the ball is on our court and they are waiting for our move.
Problem is that with FDEVs silence on this we will never know if this is true or not.
Here's the rub. Let's turn back the clock for a bit.
Remember when Horizons was first released? What was the hint there was something on the planet's surface to discover, of the procedurally generated variety? We'd see a blue ring appear on the planet's surface.
Remember how we'd find Barnacles? Ignore the blue circles and explore some rando planet in rando locations and hope to stumble upon one with no indication that there's something there.
Now... if you run missions with factions you get Tip-Offs to "strange things", usually a shipwreck or a semi-fixed installtion, usually with a "mysterious message" that leads nowhere.
Remember how you'd *actually* find mysterious things? Fly around rando systems hoping you spot an unauthorised transmission tower which is one of a three-step triangulation process.
Guardian Ruins? Hunt in rando systems, ignore blue circles.
Thargoid Structures? Hunt in rando systems, ignore blue circles.
If my point isn't being emphatic enough... what I'm trying to say is that FD are amazing at giving us a bunch of tools and systems of play which could lead naturally into discovering cool and interesting things, and proceeds to use none of them to actually enable logical discovery-based gameplay.
To address your points in-turn:
Thargoid Probe points to Merope 5C? Thing is, we *know* nothing is there thanks to the new exploration mechanics.
Col 70 Sector? We *know* Wreaken Construction operate in that sector, and typically, you get allied with a relevant faction to get a permit for their region. Getting allied with Wreaken Construction does not result in a permit.
Further, we *tried* to get into the Cone Sector, which was not permit locked, via the Gnosis. FD prevent it and permit lock the region, solidifying the fact FD want us to look at Unknown Permit Regions and *know* we cannot go into them.
The ball may well be in our court, but if it is, FD sure as hell are making whatever we have to do so absurdly unintuitive they might as well not have put it in the game. I may not be an expert in game design, but I know enough game theory to understand that your game should intuitively teach you basic mechanics that can later on be applied to unintuitive situations, like how you defeat your mirror-image in Prince of Persia. FD does none of that, encouraging you to become better and better at the various systems in the game, and completely discards them for the discovery of anything plot-related.
So yeah, as far as I'm concerned, if the game teaches me that the DSS reveals signals of interest on a planet, and there's nothing unusual that shows up on Merope 5C according to the DSS which is *meant to* tell us about all the signal sources on the planet and can discover guardian ruins, thargoid structures, barnacles etc., then there's nothing there, even if the Thargoid Probe points there. And if there is something there, then FD's done some trash-bin game design to find it.