Hot on the heels of Krita 4.2.0, we're releasing 4.2.1 today. The main fix is for the problem where painting could get slow after a while, but there are many more bug fixes: https://krita.org/en/item/krita-4-2-1-released/

oh my goodness that was so difficult to sign onto this forum.

Hello! Love Krita, always recommend it to work colleagues at the animation studio I work at. My observations as a mac user:
It works GREAT, BUT I lost all pressure/opacity sensitivity once I updated. I uninstalled and reinstalled wacom drivers, rebooted multiple times with no success. SOLUTION:

You have to purge the previous install of Krita. I just installed Krita 4.2.0 as an example, then lost pressure sensitivity from 4.1.7, same again as I updated to 4.2.1 from 4.2.0. Perhaps you only need to delete the preference files? I used an app uninstaller (I chose one from the apple app store) to completely remove everything, including the system preferences. Once that occurred, my pressure sensitivity came back and everything was cool.

I use Krita on a number of platforms: Windows 7 and 10, mac Os (High Sierra) and Ubuntu Budgie 18.04/19.04 - it's great! I especially like the appimage system on Linux, and it's ability to run multiple different versions of the same software.