He could be just about anything. A mature weight will help us to make better guesses, but the Chestnut Agouti color appears in many breeds, including those not accepting it as a show color.
I have seen Satin x Mini Rex crosses that look identical to your rabbit. Being able to feel the texture and density of the coat would be a huge help (but Ican't do that over the internet LOL)
Some breeds have a coarser coat with more guardhairs. Breeds mixed with lops will often be much softer and longer. Breeds mixed with satin have a narrow diameter to the fur shaft.
Your bunny still appears to have its baby coat.
Pam