It's all in the name :) WIP, see DEV_NOTES.md and https://docs.google.com/spreadsheets/d/1CA_RlD6NTEXU8FZAATqmE4FEGLo2nq-Fe_9v-TF6sh4/edit?usp=sharing for a compatibility list.
If you want to try it out, make sure to use the modified MiSTer binary.