How do I stop my dog from digging around my fence?

Apparently the fence is already erected, so you need to curtail his want to dig. Spraying the ground with black pepper, hot sauce and water mixture could curtail his digging. However, he probably has a lot of nervous energy, so playing with him, and giving him something like a kong with kibbles inside so he has to work at getting them out might give you both the desired effect that you are looking for. Last but not least, is buying livestock fencing and digging inside the perimeter of your fence and laying that in the ground and attacking it to your fence, then cover the part on and in the ground with the dirt. I had to do that with my wolf hybrid.

We use fireplace logs where dogs dig. We have been lucky, if ours dig it is in the yard, not at the fence, at least not the dogs we have right now.

A cat

Spray the area well with peppermint oil or orange oil, both of which dogs tend to avoid. If you need something stronger, you can try chili powder, in small quantities. These will need reapplied after rains.

Train your dogs. They are bored and not receiving enough exercise. Play ball, long walks.

https://www.rover.com/blog/how-to-stop-dog-digging/

https://www.humanesociety.org/resources/stop-dogs-digging

https://www.cesarsway.com/dog-behavior/obsessive-behavior/getting-a-dog-to-stop-digging

They just want to please you and receive unconditional love.