Eons ago when I did gigs in the park from 9am to noon the sun was in my face. I had one of those EZ up tent ma jiggies positioned to shade the keyboard and me. I still had trouble seeing my touch screen.

What really helped but didn't create a miracle is, I cut a piece of thin cardboard painted it black and put two strips of Velcro on each side of the touch screen and fitted the card board to keep the sun out. I put it flat to the back and had it folded to be higher in the front for reading. Like I said. It's no miracle fix but helps me to get by. Laptop screens are hard in the daylight too. I adjusted my arrow cursor to have a long tail trailing behind it and that helps also.