I think we may need to refocus and highlight some of the things we know.
1. The only confirmed finding of these artifacts has been from Redeye. He found these outside of a system that has any connections to aforementioned Lore, GalNet Articles, or literature. Which leads me to believe that they can be found in any system in the galaxy. Which means that unless GalNet says, "A convoy carrying Unknown Artifacts coming from x-system heading to x-system was spotted" we probably don't need to spend a ton of time moving from system to system.
2. If they can be found anywhere, we need to increase our odds of finding them. Its been said above that the higher population systems seem to spawn more signal sources than those with lower populations. I think we need to concentrate our efforts looking through these systems.
3. Once we find these signal sources, its important to make sure that we're looking at the cargo of any vessels we come across. Of the few confirmed facts we have on these UA's, one is that they were added at the same time the rest of the "make piracy more viable" materials were added. They were intended to be taken as loot by pirates. I don't doubt that we can find them floating in space, just don't pass up an opportunity by not checking the cargo of these ships.
Also, if there is a GalNet article about this, I'd hope that there would be some way to let the rest of us know if/when someone finds one and deciphers the meaning. Otherwise someone joins the hunt and then solves the puzzle the rest of us have been working on. I.E. have them put it on display at some station for a reward worth more than the UA sells for.
Fly Safe Commanders, I'd reckon the 'verse has many secrets left to share.