On The Rocks is out on audio on a couple of sites – it will be weeks yet on others (not looking at you Audible)

On Google
https://play.google.com/store/audiobooks/details/Peter_Rhodan_On_The_Rocks?id=AQAAAEDcoSnh5M

On Apple
https://books.apple.com/us/audiobook/id1560593140

I will let everyone know when Audible finally gets their act together