A technical bulletin to the main dealers would be ethical, telling them not to ask owners to come in for a diagnostic check, and wait for an update from Audi. Either the audio kit works with DAB+, or it doesn't, or will need a firmware upgrade. The poor person on the service reception can only advise the owner comes in for a check, as they are not told anything else. If it does not work with DAB+, what happens when all of the channels are eventually moved over to DAB+ ? Will your radio be useless on digital ? The UK government are looking at commencing a switch off for FM starting in 2030, 5 years away... so you wont have a radio at all....