Cosmological homogeneity has been a dubious assumption since its inception decades ago. It makes the modeling much easier and cosmologists defend it with their usual certainty.
However observational challenges to that assumption have repeatedly arisen in the form of the Sloan Great Wall, the Giant Gamma-Ray Burst Ring and the Large Quasar Group.
Now an arc of galaxies 3 billion light years long has caused the assumption of cosmological homogeneity to come under renewed assault. This structure would be 3 times bigger than allowed by the standard cosmological model and the homogeneity assumption.
Here is an article on the new research: sciencenews.org/article/galaxy-giant-arc-3-billion-light-years-long-cosmology-space
This would be a real game-changer if independently verified. Expect a cosmological battle over this. Stay tuned.