See what is written above me ^
A GPU core on MiSTer just for KODI seems like a waste to me.
There are so many cheaper alternatives for KODI than MiSTer which is really not
the sorta device or project that would work well for KODI.
It is really more suited to recreate old console and computers and arcade machines.
That $50 you have burning a hole in your pocket should go towards a nice 2Gb RAM Pi 4
and you can install RetroPi on it and run KODI and old machines on it very well, even many things
that aren't running on MiSTer.
That sounds like what you actually want....