"If you look at data from the Planck satellite, and the 2018 legacy data in particular, it shows that the CMB is being more strongly gravitationally lensed than it should be. The Planck Collaboration called this anomaly Alens, and it's yet to be resolved, but the team believes that one explanation could be the shape of the Universe. "A closed Universe can provide a physical explanation for this effect" This study suggest that the universe would be more likely closed or open than flat