I have rolled back the system generation with
nix-env --profile /nix/var/nix/profiles/system --rollback
But the default entry in the boot menu is still for the most recent generation.
How do I get it updated and reflects the rollback without modifying the grub.cfg manually (I use grub)?
nixos-rebuild --install-bootloader boot is not what I want. The system on my laptop simply cannot be upgraded, or some Qt or plasma stuff will break (issue 97157).