Hi,
Based on my understanding,
- Remove device, autopilot hash from source tenant
- Remove device (leave) from azure ad
- Disjoin from on prem AD
- Join the device to the new tenant
if autopilot is required on target tenant, reset is required https://techcommunity.microsoft.com/blog/intunecustomersuccess/support-tip-how-to-transfer-windows-autopilot-devices-between-tenants/3920555
Please note that other factors to be considered like count of users, devices, location, authentication token cleanup, certificates, local admin account, enrollment GPO, etc.
Tenant migration is not a supported scenario for Intune. The supported and recommended way is re-enrollment that may have require reset\wipe.
You can also explore migration tools to migrate devices along with user profiles. Also, start with test migration to capture the environment specific dependencies, experiences.
If the above suggestion helps, please click on 'Accept answer' and 'upvote' it.