Are all files gone from efi partition? Early Ubuntu UEFI installs used to delete Windows efi and install its own efi, but that was fixed a year or more ago. Or did it just change default in UEFI back to Windows?
Do you have an entry in UEFI for efi shell? That also has many functions which I know little about.
You do not have a backup of the efi partition? If you ran Boot-Repair you actually do have a backup somewhere on your system of most if not all of it.