finally I managed how to install all under Ubuntu 18.04 to use GNUradio-Companion and GQRX via gr-osmosdr !!

Well after all is quite simple if you follow some "clear instructions" and "how-to" ......... next week I will try it also under Ubuntu 16.04 ... need some manual adjustement .........
Just need to solve a problem with RSP-2 (multiple antenna input) and GQRX. How to switch between input using gr-osmosdr driver ?????
Regards, Pietro