Veeam's RnD team has performed extensive testing with Veeam Backup & Replication 12.1.2 (build 12.1.2.172) and has determined that it is functional with vSphere 8.0 U3; however, the following limitations apply:
 

Automatic vCLS VM Exclusion Broken

The automatic exclusion of vCLS VMs does not occur after upgrading to vSphere 8.0 U3. This automatic exclusion feature, first introduced in Veeam Backup & Replication 10, fails to function because vSphere 8.0 U3 changed the VM type identifier for vCLS VMs.

Advice: Use the provided workaround until Veeam Backup & Replication 12.2 is available.

• Challenge: If a container object (e.g., Folder, Cluster, Datacenter, Host) has been added to a job, that job will attempt to process the vSphere Cluster Services (vCLS) VMs. The tasks for those vCLS VMs will fail.
• Cause: In vSphere 8.0 U3, the vCLS VM type was changed.
• Workaround: Add the vCLS VMs to the Global VM Exclusions list to prevent the jobs from attempting to process them.
• Resolution: This issue will be addressed in the upcoming Veeam Backup & Replication 12.2 release.
   

NSX-T 4.2.0 Compatibility Untested

Due to a lack of access to NSX-T 4.2.0, compatibility of NSX-T 4.2.0 and vSphere 8.0.3 has not been tested with Veeam Backup & Replication 12.1.2.

Advice: Customers are advised to await further testing results before deploying in production environments. Testing will be concluded before the next Veeam Backup & Replication release (version 12.2).