To use UEFI in libvirt/qemu add this to /etc/libvirt/qemu.conf:
nvram = [
    "/usr/share/ovmf-x64/OVMF_CODE-pure-efi.fd:/usr/share/ovmf-x64/OVMF_VARS-pure-efi.fd",
    "/usr/share/ovmf-x64/OVMF_CODE-with-csm.fd:/usr/share/ovmf-x64/OVMF_VARS-with-csm.fd",
    "/usr/share/ovmf-x64/OVMF_CODE-need-smm.fd:/usr/share/ovmf-x64/OVMF_VARS-need-smm.fd",
    "/usr/share/ovmf-ia32/OVMF_CODE-pure-efi.fd:/usr/share/ovmf-ia32/OVMF_VARS-pure-efi.fd",
    "/usr/share/ovmf-ia32/OVMF_CODE-with-csm.fd:/usr/share/ovmf-ia32/OVMF_VARS-with-csm.fd",
    "/usr/share/ovmf-ia32/OVMF_CODE-need-smm.fd:/usr/share/ovmf-ia32/OVMF_VARS-need-smm.fd"
]

And restart libvirt. Now you should be able to select UEFI firmware in
virt-manager.