You could try using a bootable USB stick with a Ubuntu Live ISO running.
Then you can copy the correct files manually to LE's boot partition on the HDD/SSD.Or take out the HDD/SSD from your htpc and put it into a different PC.
If you're without Linux skills, then it's probably best to do a fresh, new installation onto your PC.
Doing a spring cleaning install of Kodi has its perks anyway.
Thanks, I was able to make a libreelec bootable usb and it worked great.