Got it working after I failed at every attempt, when first starting with a system migration from an Intel based Mac running the same macOS. Moved from a 2017 4.2GHz i7 iMac to a current M2 Max 12 core Mac Studio.
Didn't matter what I did or removed with the original build from the Intel Mac migration. Had to start from scratch. Installed Ventura after a drive erase. Set up a user account with no cloud anything, as simple as possible. Then updated Ventura.
Rebooted in recovery mode to set "Reduced Security" with the "Allow user management of kernel extensions from identified developers" option checked.
Rebooted and installed the latest MOTU (April 2024) audio driver for the 828es, following MOTU's instructions. Allowed the system extension and rebooted. Works just fine, USB and Thunderbolt.