I've read castor oil works, but here's a link with ideas for you:
Use an effective castor oil-based repellent to drive armadillos out and to prevent them from digging for food on your property. Castor oil is an all-natural oil that penetrates the ground, and repels armadillos in two ways: spoils the food sources (insects, grubs, etc.) underground, making them unpleasant to eat.
We have used these tips for armadillos too: https://chemistrycachet.com/how-to-deter-animals-from-flower-beds/