Clean the EFI partition

Remove unused boot entries

Go into /boot/efi/EFI and see what’s in there. There should only be the bootloader for your Linux installation showing. If you do this in Windows it will also show the Windows boot loader, don’t mess with that!

On my system it looks like this

root@queeg-500:/boot/efi/EFI# ls -l
total 8
drwx------ 2 root root 4096 Aug 14 22:49 2
drwx------ 2 root root 4096 Aug 14 20:03 debian

And inside the debian folder is

root@queeg-500:/boot/efi# ls -l EFI/debian/
total 5208
-rwx------ 1 root root     108 Aug 14 22:53 BOOTX64.CSV
-rwx------ 1 root root 1206824 Aug 14 22:53 fbx64.efi
-rwx------ 1 root root     126 Aug 14 22:53 grub.cfg
-rwx------ 1 root root 1529200 Aug 14 22:53 grubx64.efi
-rwx------ 1 root root 1261192 Aug 14 22:53 mmx64.efi
-rwx------ 1 root root 1322936 Aug 14 22:53 shimx64.efi

These are just files and folders, and can be removed with the usual tools. Be careful, removing these will stop your machine from booting! However, your machine isn’t booting at the moment, so it’s unlikely to make things worse.