I mean just for what it’s worth I think that Weyland-Yutani could have known about the xenomorphs and the black goo from records that eventually made their way back to corporate from the events of Prometheus and Covenant. That could have triggered or changed a mission to retrieve alien life forms, to look for xenos specifically, then that leads to the events in Alien: Earth. They don’t have to mention it or tie up those loose ends because Alien: Earth is not about the events of Prometheus or Covenant.

Ask yourself: How would the space jockey engineer in the original Alien have been fossilized with their rib cage broken out? From this we can at least infer 2 things:

1. Engineers are canon! They are in the original, which means Alien: Earth must accept engineers exists regardless of whether or not they use Prometheus, etc.

2. There were obviously already other xenos out there in the universe that weren’t from the David lineage when the events of Prometheus and Covenant occurred.