Deutsche Übersetzung kommt !
I backed up my iTunes library (the entire „iTunes“ folder)on an external hard disk.
I installed Catalina on a newly reformatted hard disk on my iMac.
I copied the backed up iTunes library into ~/Music (Home folder → Music).
I launched the Music app. It showed my handful of iTunes purchases, but not my playlists nor the music I had ripped from CDs. 🤔
The key was in how you open the MUSIC app:
Hold down the OPTION key while opening the MUSIC app. You will see a dialog box.
Pick the option „Choose Library“.
Now, navigate to your ITL file (not XML) for the old iTunes database you want to import and double click it.
The MUSIC app will then ask you to Save this as a new Music Library.
Give it a different name than your other library(s).
Pick a location etc.
Once that is done, you still have one final step – to change the default directory of your actual music files.
Go to MUSIC preferences, select Files directory, and change it to where your actual audio files are.
MUSIC app will then ask you to organize, click YES.