grub-live broken in Whonix 16 has been Released! (Debian 11 bullseye based) - for VirtualBox - Major Release.
Actually required…
Debian bug report:
kernel command line (grub) UUID=... and PARTUUID=... Can not mount on filesystem /run/live/rootfs/filesystem since Debian bullseye
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=994138