I have created some nice dual boot images for LibreELEC + Lakka.
NOOBS Lite + LibreELEC + Lakka
(Available for all Raspberry Pi versions)
Included in LibreELEC is a simple add-on that reboots into Recalbox.
Lakka has also been setup to boot back into LibreELEC when you exit it.
The changes to each OS are minimal (a basic add-on added to LibreELEC & autostart.sh added to Lakka).
This allows for updating either OS (manual or standard methods) without affecting the dual boot
Get the dual boot images here (video and written instructions available):
[How To] Lakka & KODI Dual Boot
If you prefer Recalbox instead of Lakka, see my other post HERE