I also activated 'GRUB_DISABLE_OS_PROBER=false' so Ubuntu is also taken
along, for all cases (so said in germany...).
Then this process is finished for me and I thank you for your help,
Christian
Am Mittwoch, dem 27.12.2023 um 11:15 +0100 schrieb Pascal Hambourg:
Basically, the Debian installer just installs required grub packages and
runs grub-install and update-grub in the target system environment so if
GRUB loads and displays the menu, it is unlikely that the installer did
something wrong.
After booting into Debian through Ubuntu's GRUB menu, you can try to
re-run these commands and reboot with Debian GRUB. If it does not fix
the error, then the issue probably lies in GRUB itself and the bug
may be reassigned to grub2.