Hi, I'm going crazy over the same issue... New iMac with OS Catalina 15.5.5 and no way to open Photoshop Element 2020. Following the steps described above gives me the following error in the Terminal window:
objc: Class CVSlider is implemented in both /Applications/Adobe Photoshop Elements 2020/Support Files/Adobe Photoshop Elements Editor.app/Contents/Frameworks/libopencv_highgui.2.4.9.dylib (0x11c188ea8) and /Applications/Adobe Photoshop Elements 2020/Support Files/Adobe Photoshop Elements Editor.app/Contents/Frameworks/libopencv_highgui.3.1.dylib (0x120025ed0). One of the two will be used. Which one is undefined.
How to solve this?
I already tried removine one of these files, without success.