It seems my old thread has gotten itself archived (due to lack of interest):
https://www.mobileread.com/forums/arc.../t-177954.html
The first release was made April 30th.
The second release is now in pre-release testing:
https://www.tizen.org/
To begin a port to the Kindle e-ink machines, start with the information on this page:
https://source.tizen.org/documentation
And if your Kindle ends up looking / acting like a Samsung Galaxy series device . . . .
Well, at least you will not be able to blame it on Amazon (or any other closed source vendor).