We fit an exponential distance-redshift model to the Pantheon+ dataset of 1701 Type Ia supernovae. With two parameters, the model achieves χ² = 688.67 vs ΛCDM's 684.60 (Δχ² = 4.07), rendering them statistically indistinguishable. Models diverge at z > 5, testable with JWST.
Jason W. (Sat,) studied this question.