Right … I read “(Post Install)” as “Installation completed successfully” … but you are right, that during the installation, the initial setup insists on starting the cubes and that can break the installation process. Sorry for suggesting changes that wasn’t relevant for you situation. :-/
In my case it’s a Lenovo T14 Gen 3 (w. AMD Ryzen 6650U), where I currently need to limit the number of vcpus to 1, in order to have the cubes start - so I know the “Quick! - make the change to the cube, before it’s started”-race with the installer … and I have done test installations on an USB stick in a different machine, in order to work around the initial setup.
For others, I found the process was suggested in:
and the qubes.skip_autostart documented in: