If one ear drifts down to the side, it means there is likely some lop mixed in there somewhere. The lop gene affects the cartilage and muscles at the base of the ear. A full lop bunny can technically lift their ears up, but it takes a lot of effort because there isn’t something “solid” holding them up. It is easier and more natural for them the just let them hang. When it comes to lop mixes, they will have varying amounts on control over their ears. This means you can have one ear up and one down all the time (or helicopter ears) or you can have both ears up all the time and one will lop when bunny is relaxed.
When I look at your bunny, I see the shape of a Holland. The head shape, the rounder body, etc. are similar to a Holland. But since he’s a mix, the resemblance isn’t spot on. Also, the shorter and broader ears are characteristic of that breed. Am I 100% sure he’s a Holland mix? No. But that is what I see when I look at him.