CoreElec uses kernel 4.9 (vendor kernel) which has all the GPU/VPU features included. Same time ago I ported CE media drivers to a “similar” Ubuntu kernel (Odroid N2+, https://github.com/beta68/linux). This was already a huge stunt and I “only” was able to use KODI within UBUNTU in a chroot environment due to missing libMali sources. To my opinion it does not make sense to port 4.9 CE media extensions Radxa to a mainline kernel. This would take years and this Mali GPU will be old before any new kernel release date.
The only way I found I described here: HOWTO: KODI, VDR, ambilight, UBUNTU and X11
Kind regards,
beta