I have tried both 2020 and 2021 and suddenly Photoshop does not respond to which tool is selected. When I have the direct selection tool selected, its no longer a black arrow. It appears as if the paint brush is selected and you can even change the "brush size" with the brackets. Even though just the direct selection tool is selected. This is the case whether I am using my mouse or my XP-Pen tablet.
Also, if I try to use the Stamp Tool, I can no longer sample at all: If I option click (using the pen tablet or mouse) It doesn't sample anything and thus doesn't paint anything.
The brush tool doesn't work either, it just erases no matter if I have it on foreground color or background color. Also the paint brush will no longer sample a color.
I have tried trashing the preferences and uninstalling/reinstalling.
After using photoshop for the past 22 years, I have never had so much trouble with it.
As a follow-up, I decided to apply a Mac re-start to the system and then re-launched Photoshop. It appears that the above problem has now dissappeared - at least for me anyway. Perhaps this info is of use and worth trying as a fix.