Can you give him an old t-shirt? Sticks from outside?
Is he getting out enough energy during his peak active hours? Does he have enough space to run around? When my rabbit starts to get restless and/or destructive, I take her outside for a long walk. (use extreme caution!)
Are you constantly doting on your rabbit-petting them enough, etc? (no judgments, just wondering because sometimes rabbits get restless when they need more attention)
Are they food motivated? I will sometimes hang veggies from clothes pins on some string and mine loves to stand up on her back legs and reach for the food. You can also try hiding some treats around your house.
I can understand your frustration, since it took me a long time to figure out what makes my rabbit tick. For her it’s having enough space to run around, lots and lots of attention, (seriously i’m always on the floor). Also, try giving her more places to hide. She likes cat tunnels, chasing t-shirts, going outside, and there’s this little cat toy she likes: it’s a ball made of straw. It has some beads inside of it, so it does make some noise, which keeps her interest.
Are you rotating the toys? Sometimes rabbits lose interest if you just throw down a bunch of toys. Rabbits are investigators, so there has to be constant novelty.
That’s all I can think of off the top of my head. Sorry if it wasn’t helpful. I hope it at least got ya thinking!