On some AMD Ryzen X570 (Gigabyte) motherboards, virtualization is
disabled in the UEFI firmware (BIOS). If are having trouble running
qemu or virtualbox, the kvm module is loaded, and lscpu indicates
that the CPU supports KVM, go into the BIOS, Tweaker menu tab
(advanced mode), find "Advanced CPU settings" and enable "SVM mode".

On some boards, you can find the KVM settigs under "Advanced CPU Core
Settings" option group, under M.I.T tab - "Advanced Frequency Settings"
option group - frequency settings - CPU core settings.