How to remove default LXD storage?

The default storage can be deleted with sudo lxc storage delete default.

The default storage cannot be deleted because it is part of the default profile. The default profile cannot be removed. So the way around this is to push a blank profile to the default profile with;

printf 'config: {}\ndevices: {}' | lxc profile edit default

Then the default storage will be removed from the default profile, so you will now be able to remove the default storage with;

lxc storage delete default