I’ve seen @PatriciaTegtmeier editing a couple German audio dramas.
Examples:
Artist credits include: Author(s) and audio drama adaptor with a German join phrase meaning “adapted from [a novel by]”
I find that approach quite sensible. Release (group) credits could look like this:
[Adaptor(s) adapted from] Author(s) [starring performer(s)]
or
Author(s) [adapted by Adaptor(s)] [starring performer(s)]
Actual join phrases from cover should be preferred.
Only question that remains, what about character names written on cover, include or not?