Mike Ruhe has a patented fret system which he claims provides better intonation for nylon string guitars. He explains it - in German - in this article below.
https://www.ruhe-gitarren.de/en/patented-fretboard/
https://www.youtube.com/user/mdadoc
Greg Byers, a famous luthier, wrote an article about classical guitar intonation back in the 1990s:
https://www.proguitar.com/academy/gu...yers-classical
Here is a discussion on the Delcamp forum that mentions and comments on both of the above, as well as other comments:
http://www.classicalguitardelcamp.co...ic.php?t=52446
And then there is Earvana:
http://www.earvana.com
Best wishes!