Grounding an MPPT controller

I would connect solar controllers ground to the RV frame,
If I bothered to connect it at all,
I would Not connect it to battery shunt
Ground in this case is for lighting protection and would goto earth ground when used in a stick house install, it does NOT equate to battery negative that everybody likes to call ground, but is really the common return for Current flow,
Solar controllers often use the negative terminal as the switched 'charging control' and the positive as the common,
Incidentally IIRC
The Earth is actually positive charged and the clouds are negative (Static charge from atmospheric friction)
Some early automobiles used positive as common to the frame (aka ground) and Negative as the Hot wiring, which is more electrically correct, as electricity aka ELECTRONS travel from Negative to positive, Not positive to negative,
But of course obstinate USA engineers had too do things different than Britton and Europe, so we use a system that have people thinking backwards, and more galvanic corrosion at body parts and electrical connections than would happen if car body frame were at positive potential instead of negative potential
Whoops....according to NOAA I got sky and earth potentials reversed, sky/clouds are positive and earth is negative
So much for My old memory

Thanks for the info FWC! Wasn't sure if there was a potential to create a ground loop or something that might cause problems. Much appreciated!!

The ground on the MPPT is not all that important in a mobile application, so it it fine to tie it to either side of the shunt, or to the battery negative, or to a negative bus, which ever is most convenient. No current will flow on this wire.

Are you talking the negative connection? It should go to the battery or to the battery side of the shunt.