Vmware Fusion 12.2 on Big Sur 11.6
With Side Channel Mitigations enabled, provisioning and installing a Linux Mint (20.1 or 20.2) works fine, but once I try to do a system update within the VM, all sorts of signature checks fail, making updates impossible. I was chasing my tail thinking it's the Microsoft Defender antivirus running on the host OS, but it turns out, if during provisioning of the VM (before installing the guest OS) I disable Side Channel Mitigations, all goes fine.
I recommend you all disable Side Channel Mitigations until Vmware identifies and fixes the underlying problem. I think this should not be enabled by default, at this point.