After identifying target computers enrolled via PreStage enrollment that do not have volume owners, you can erase and re-install macOS. This will install macOS 12.0.1 which allows you to re-enroll the computer via a PreStage enrollment and set the Recovery Lock password during enrollment.
To erase the computer, send the Wipe Computer remote command. For more information, see Remote Commands for Computers in the Jamf Pro Documentation. After wiping the computer, you can re-install macOS. For more information, see the following articles from Apple's support website:
After the computer is erased and macOS is re-installed, you can re-enroll the computer in Jamf Pro. For more information about PreStage enrollment, see Automated Device Enrollment for Computers in the Jamf Pro Documentation.