Here is a list of split keyboards I'm aware of. This is a frequently requested info on r/mk. Filter keyboards by development stage, size, features like Bluetooth, staggering etc.
My approach to handwiring. Another frequently requested guide.
The GOLEM evolution model
This is an evolution model for optimizing logical layouts in Hungarian. Letter frequency, bigraph and trigraph statistics. This was my original area of interest and the main reason to start this site.