Installing Big Sur as guest on Parallels

Tried with a fixed disk and got the same issue.
Then, I tried with Virtual Box. There, it started in verbose mode automatically (like always with Virtual Box, go figure), eventually showed the welcome screen (“Choose your language”) and was stuck like with Parallels Desktop (mouse integrated in the VM, but wouldn’t react, like the keyboard).
Now I know it’s not specific to Parallels.
I downloaded the Beta installer twice, so it’s not because of a corrupted installer. Hard to find what remains possible…

My next attempt will be to try on another computer (a 2013 MacBook Air) using Virtual Box. Parallels Desktop is hardly an option on multiple computers.