Hello,
If I am not wrong there is no alternative for the moment (concerning IMEI / SN pre-registration)
But google said that on an article:
https://www.business-standard.com/article/technology/google-android-12-to-enhance-privacy-productivity-for-work-devices-121021900313_1.html
For employee-owned managed devices, we're creating a new enterprise-specific device identifier that may help enhance privacy in the event an employee leaves their current employer.
"Instead of relying on hardware identifiers such as IMEI or serial numbers, personal devices will get a new identifier derived programmatically during enrollment," Google said.
The workaround (less secured) is maybe to create a specic group for device restriction (but it will be based only to user not the couple device ID / user).
Best Regards.