Wow, you are fast, thank you !
When I leave secure boot disabled, I can see the GRUB boot screen with "kali - boot non persistent mode, Kali - boot persistent, Kali Failsafe, Kali forensics...".
When I chose the first one (I tried them all, same result), I have this message :
"Booting 'Kali - boot non persistent mode'
Secure boot not enabled
_"
And nothing else. Any idea ?
