I think you have two options-
1. Shoot only RAW
2. Use the OS to manually copy only the RAW from the SD, then import.
The Lightroom 'mantra' is to be "non-destructive", it does its best to prevent you losing images- as you might if you did not import the JPGs from the SD.
Yes, I suspected your proposal was the only way. what a pity.
Maybe I used aperture and capture one fear too much/too long - and now everything works completely different.
thanks a lot.