Installing Big Sur as guest on Parallels

And yet it happens to me 2 of 2 times…
I’m aware my configuration isn’t officially supported (Mojave running on a 2008 Mac Pro), but I fail to understand how this could be related. That’s the only thing I expect to be “rare” enough on my setup resulting in no one experiencing the same issue. I don’t have a supported Mac at hand anyway.

I’ll try again, re-downloading the installer, perhaps…

Thank you, Douglas, for all your suggestions and help.