sda1 is mounted as /boot/efi. sdb1 is not mounted at all (or mounted to some other mount point). apt-get can cause new files to get installed in /boot/efi.

Set “All files” behind “File type.” Go to the folder “EfiBoot” in which the file “bootx64.efi” must be located. Then open the folder “EfiMicrosoftBoot.” ...

3] Try to boot your computer from bootx64.efi file or bootia32.efi file manually Some users have reported that the issue was fixed after manually booting their computer from bootx64.efi file.

The researcher's analysis of the bootkit.efi file determined that Lenovo devices based on Insyde are the most susceptible, as Bootkitty references specific variable names and paths used by this brand.