I installed Krita 5.0.2 on my Windows 10 machine to test it with my old Wacom Intuos 5. The first attempt lasted only a few minutes because Krita was flickering again and again which made working with it impossible. First I thought maybe my old tablet has an issue but after unplugging it and even restarting the host machine Krita continued to flicker.
After some research I read about changing the renderer in Settings > Configure Krita > Display > Canvas Acceleration. This was set to “Direct3D 11 via ANGLE” by default. I changed it to “OpenGL” and restarted Krita for the setting to become effective after realizing that the active renderer stayed the some after ack’ing the dialogue with Ok. Et voila, after the Krita restart the flickering is gone.
Hope this helps others with the same or a similar problem.