There should be no difference. We use the same image for all RPI device. But keep in mind, Debian Bookworm is flagged as testing still. As well our migration script might not 100% bulletproof. Create a backup/clone before going that way.
unbound 1.17.1 for bullseye-backports is already out since last month. It can be installed from backports repository but Iām not sure if it breaks the DietPi version of unbound.
There is no DietPi own version. We install unbound from official Debian repository. Therefore, Debian backports should work same way as on every other Debian system.