Just a footnote to this.
My newly arrived VU Duo 4k SE, loaded with pli 9 from a very recent overnight build, worked fine without any special configuration with the Kabelio CAM (in other words using the same SW as the Zgemma H7S). My conclusion would be that if you intend to use Kabelio I would not buy a Zgemma H7S.
Many thanks in particular to Bloke76 for the very useful input and of course to the other contributors.