I haven't looked and not logged on to check but was the Zurara bubble side of the Rift bases or Rim side?
As to Conflux and Gap, I doubt we have other megaship wrecks there. The plan was to destroy the ships and evidence and it seems unlikely that they failed all 3 times.
I think we only have 2 main things to look in to which is how to get into the Col 70 permit bubble and the area they were actually scouting and dropping terraform packages in the rift. Once we have a rift location in relation to the bases there we can extrapolate a search area in conflux and Gap, but it would be more difficult there.
For guardians, I still think their genetic tech is linked to barnacles and other lifeforms that seem linked to Nebulas for life on otherwise barren worlds so we will often find signs in nebula areas, and I suspect Thargoids are their creations with some inherited tech.
I also suspect inra, the powers and some major corporations have been involved in reverse engineering that tech also. In fact our current FSD tech likely came from that.
So I think guardians will lead to new tech or at least Engineers mods and the history of Thargoids. Col 70 will lead to corporation work reverse engineering and secret fleet building, the rift, gap and conflux will lead to intended or existing long range mini bubbles, and they will all lead to Thargoids or other aliens.
That's my tinfoil moment, and can only see Col 70 sector and working out where Zurara dropped its packages as being the only clues we can follow while leaving those Cannon people to sort the guardians connection, and hope FD have already put what we are trying to find in game.
As an aside, finding the rest of the generation ships may be fun and could open up something new although it is only looking like the dead ones so far.