Being burrowers, rabbits dig. And dig WELL. It’s a natural instinct, no cure for it. Some dig more than others. If I can make a suggestion, try getting your bun a sturdy cardboard box (Food grade, make sure it hasn’t held chemical products or cleaners), and half fill it with semi shredded cardboard strips and shredded paper, and let them go to town in it.
And unfortunately, despite being very clean and fastidious creatures when it comes to grooming, rabbits can be absolute SLOBS when it comes to food, hay, litter and toys. Loki is a very neat and clean bunny, and doesn’t chew anything he’s not supposed to, once he got past puberty, but when it comes to his food, it goes EVERYWHERE when he’s searching for his favorite bits. Even if I put said bits on top. He always has to check the bottom in case I hid something, he thinks. And his litter pan, being huge, because he’s a Flemmie, still isn’t big enough to contain his litter because he insists on rearranging it after I clean it every day. Which I’m sure is his commentary on my cleaning skills or something. But he’s simply got to dig it out, push it around, until he has ramps in two corners for him to rest his chin and front paws on. Which means litter over the sides of the pan, and all over the floor for me to clean up. I just sweep it up and dump it back in, if he’s not in it, or on top of him, if he is. If he is, he grumps at me, shakes it off, and rearranges it. Again. It’s funny to both of us.