I spent hours after each Photoshop Update trying to solve the problem. Installing, removing, cleaning, reinstalling etc. At onr point I made a second account on my mac and voila, I was able to start Photoshop 2020 without the problem. It turns out, that when I disabled all of my user-fonts in Font Book it started to work in my main account. Obviously there was a conflict with an installed font... Maybe that can help somebody else too....