I suspect that any whole grain wheat flour will work fine. The question is which ones will need a little more liquid and which less. Off the top of my head, you can probably drop the extra water with einkorn, but you might need more with blue emmer. The red wheats would probably be the same as kamut or maybe a little more.
If you find that hydration is fine but the final product is a little crumbly – because of a lack of gluten in the wheat you choose – you could switch to the egg and oil amounts of the gluten-free biscotti recipe and that should bind things up nicely.
I’d love to hear about the wheat you use and the outcome.