Hi Sven,
I just did quick test and was able to enable Microsoft Entra Kerberos on general purpose V2 LRS account using Azure portal without error.
Are you using portal to make the change or other method (CLI, powershell, REST API, etc.)?
Any differences between your case and my test?
If you create a new storage account and test enabling it on that, are you successful or does it fail? You can delete the storage account right after testing.
-TP