After many repeated flights..
The 750 and the 530 did not display LPV. They displayed RNP (sorry - my bad)
Tried the same approach with the Duke. The 750 displayed RNP, same result - no GS indicator
Tried a different approach. This one displayed L/VNAV on both the Duke and the TBM
Approach worked a treat.
So if it says RNP in the approach, I know it's not going to work.