It is always better to use the latest version for testing this feature.
If I remember correctly 4.2 contains some fixes for incremental backup so better to use it.

On Wed, 10 Jun 2020 at 11:28, Gianluca Cecchi <gianluca.cecchi@gmail.com> wrote:
On Wed, Jun 10, 2020 at 10:18 AM Eyal Shenitzky <eshenitz@redhat.com> wrote:
Hopefully yes, just validate that the libvirt version is >= 6.0.0.


While do you confirm that Qemu 4.1 vs 4.2 is not essential for the feature?

Gianluca



--
Regards,
Eyal Shenitzky