Not exactly. Sorry for being ambiguous yesterday.
If I click on sync now button in WiFi Sync, the app asks for the permission to access the storage. In this dialog, I see all the folders that are saved on the internal storage, so everything is fine.
However, the "use this folder" button is greyed out when I'm on the "root directory" level, according to Android 12, this is due to security reasons.
If I now try to select the "Musik" folder in that the music is stored, the app tells me that this is an invalid folder. The verbatim error message is:
"Folder "Musik" is not valid.
You must select the SD card root folder and note one of it's subfolder.
As I have already mentioned, the folder "Musik" is stored on the internal storage and the button to select the internal storage root folder is greyed out.
I have tried deleting all the app data and re-installed the app, but the result is still the same.