Thalia does sell German language DRM free audiobooks.

The big problem is that there isn't a store with a good selection in both languages at the same time (other than audible that is). So you'll have to spit your shopping habits between two or more stores, which makes the subscription offerings a lot less attractive.

Besides Libro.FM (not EU) that I know of, DownPour is another option though I believe its also not EU.

Libro.fm

https://pocketbook.de/ offers a filter to display only DRM-free audiobooks

Annas Archive…

There is no shame in getting a DRM free copy of stuff you already bought.

Thalia gives you drm free mp3 downloads.

/edit: it is also quite easy to download and remove the drm from audible (look up Libation)

Just buy a CD and rip it yourself.

Bonus: You have the backup media already.