When there are UEFI entries missing for your Linux operating system, you can add them easily with efibootmgr:

As root: efibootmgr -c -d <disk> -p <efi-partition> -L <entry-name> -l <loader-path>

For example: efibootmgr -c -d /dev/nvme0n1 -p 1 -L "debian" -l "\EFI\debian\grubx64.efi"

It will use /dev/nvme0n1p1 and on it the file /boot/EFI/debian/grubx64.efi and add it to the UEFI boot menu. On next restart, the entry should be there.

NOTE: You have to replace "/" with "\" for the loader path.

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