I just want a clean install to replace my slightly broken Kodibuntu.
If you want to replace KodiBuntu, why do you need a dual boot setup?
Anyway, the OpenELEC article is a little outdated but the basics are still correct.
In short, these are the following steps:
- Use Gparted to resize the Kodibuntu partition. Resize it 9 GB smaller
- Create a system partition of 1 GB in EXT4 format
- Create a storage partition of 8 GB in EXT4 format
- Remember the device numbers of both newly created partitions
- Copy the system files of LibreELEC into the system partition folder
- Edit /etc/grub.d/40_custom and add the LibreELEC menu entry
- sudo update-grub2 to finalize the menu changes
- reboot and hold left-SHIFT to see the GRUB bootmenu