It has to be a different race:
- Spark couldn't decode the signal it emitted
- The array had only been (relatively) recently fired, none of the archived species were then advanced enough to reach it.
It's plausible that it's surviving Precursors, but from memory their tech/architecture was always black. Hopefully something interesting comes out of it and sooner rather then later.
It's interesting enough to note that in conversations of the universe, Spark says other species had visited the installation before the Covenant but simply observed and left.
I do wonder what happened to the space fairing civilization. Since it would be very strange if there was this massive civilization that existed pre-Covenant that no one ever found out about, more so if it still exists.
I wonder if this will be a major plot point in the later games/novels? What happened 40,000 years ago that resulted in a ship crash landing on a Halo ring?
The only thing I can think of was that there must have been some major war or something that led these new aliens to go extinct at the very least into hiding. Did they stumble upon Prometheans outside Requiem and they destroyed the unknown aliens?
Now, this is a wild off theory but... Maybe it was a Human ship? How? No idea, but maybe a section of Humanity didn't get de-evolved and managed to escape the galaxy, when they came back, they had changed a lot and something happened when they reentered the galaxy, hoping that some species would find them, they used the ships becon.
It would explain why the ship had the exact or similar atmosphere to the Halo ring. Though considering how many other species breath oxygen, it's kind of a moot point.