I think there was one step missed here, and that's checking whether the BIOS is set to handle virtualization. It's a setting in the BIOS, not the Kernel, so it can't be changed in the CLI. You have to preset in the BIOS and then restart the machine. Then you set up the rest of the steps. Otherwise virtual box and similar VM tools won't work. This is a critical point for older machines because they older mother boards like the B450 tend to be wonky with virtualization settings. Usually boards afterwards at the B550 level handle it better.