Do you think it is possible to fly a P3S without a screen on the RC ?
Just for practice flying, no filming of course.

Of course, just stay close and download this...
https://www.faa.gov/uas/where_to_fly/b4ufly/

Yes, but why would you. No battery % or volt readout, No error messages by text or audio, No GPS cords. in case it going missing to name a few.

It's possible, but you do want to be careful when flying and retain LOS.

I bought a second P3S without camera just for practicing and pure fun.  You need to see the charge indicator at the battery so do not fly far away. BTW,  It will be much more "agile" in flight without the camera weight and the flight time per charge will improve too.  IMO, Way better than the simulator!

I had a XK Detect X380, it didn't have a smart battery or a camera attached for FPV. However I knew from the manufacturer you could get 25 minutes on a battery fully charged. I clipped a little timer with an alarm on my RC and set it for about 17 minutes to be safe. Never had a problem. It did have bright lights that blinked when the battery was low and I always kept in line of sight.