Did you download version 6.6 as it seems you specified in your virt-install command?
The error Size must be specified for non existent volume ‘haos_ova-6.6.qcow2’ seems (to me, at least) to say that this file (haos_ova-6.6.qcow2) does not exist.
That’s also a quite old image at this point, so perhaps you need to change that version number in your command (see the first paragraph under 3 - Install HassOS VM detailing this)