Enter the virtualenv and run Django shell:
cd /srv/funkwhale/
source virtualenv/bin/activate
./manage shell
Import Funkwhale models:
In [1]: import funkwhale_api.music as music
Select library to remove (get primary key from e.g. Django admin):
In [2]: bad_library = music.models.Library.objects.get(pk=41)
Verify that it's the library you're looking for:
In [3]: bad_library
Out[3]: <Library: Free Music Archive>
Delete library (and related objects):
In [4]: bad_library.delete()
Exit the CLI:
In [5]: exit()
Prune library to get rid of "dangling" tracks:
./manage prune_library --albums --artists --tracks