LQG (loop quantum gravity) predicts the minutest dependence of the speed of light on frequency, which would be best detectable on large populations of high-energy photons with very long astrophysical paths. A good candidate to test this would be a very far away (=> very early) gamma ray burst. GRB 221009A stepped forward some years ago. From: Stringent Tests of Lorentz Invariance Violation from LHAASO Observations of GRB 221009A Although this doesn't totally do away with LQG, it s