With the latest firmware (Ryan updated a couple weeks ago) it is possible to get this working with just Configuration.h and Configuration_adv.h, no changes to any cpp files are necessary.
There does appear to (still) be some weirdness around Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN, and as far as I know this must be disabled (even if using the zmin connector on the board).
My configuration (including other stuff specific to my machine) has G38 working and is outlined here: https://www.v1engineering.com/forum/topic/running-ryans-latest/