Has anyone rebuilt Prusa3D firmware for the Genuine Pruse i3m3s? With no answer to my question two days ago about how the Prusa printer behaves with an intermittent open or shorted thermistor, I'd like to ask this question of relative last resort.

Prusa seems to have some version of their i3 software posted on Github.  Should I expect this to be current, or some older version?

Have you rebuilt, reflashed, and operated with rebuilt Prusa firmware?

If so, what tips would you offer?

I ask because once I open something like that up, I inevitably am seduced into making changes.
The Prusa Firmware on GitHub is the very latest version -- it's the code repository Prusa uses for development.  My suggestion is that you don't use it unless you're planning to do firmware development or testing, because like any such software, it tends to have bugs.