AN 3.76 appears to say becoming is "kamma ripening" and, for kamma to ripen, craving provides the moisture. Given an Arahant has ended craving & becoming (which are both "asava" or "mental defilements"), it would appear kamma is not ripening or fruiting for the Arahant.
AN 6.63 says the Noble Eightfold Path ends kamma. Since an Arahant has fulfilled the Noble Path, it would appear old kamma is not ripening or fruiting for the Arahant.
SN 12.37 says the five aggregates ("kaya") is not-self and that it should be seen as "old kamma" that is to be "felt" rather than identified with. Since the "kaya" is not identified with but merely felt (as Arahants experience feeling at sense contact), surely there is no becoming (per AN 3.76) therefore there is no kamma ripening or fruiting when Arahants experience merely what is felt.
MN 86 (possible mythical fake dhamma) is often the go-to sutta for the old kamma adherents. In MN 86, it appears quite obvious it was not Angulimala watering & fruiting his old kamma (given AN 3.76 says "craving is the moisture" but Arahants are free from craving) but the anger in the people who stoned him that were fruiting kamma. For example, that King Pasenadi forgave Angulimala (unlike the stoners) shows the reactions towards the Bhikkhu Angulimala were not related to internal fruiting of kamma. Surely, we cannot say "forgiveness" is a fruit of the evil kamma of mass-murder.