i upgraded from 18.04 MATE to Ubuntu 20.04 MATE. After upgrading the graphics are unstable. I tried a live version of 20.04 from a USB stick and got the same result. Ended up reinstalling 18.04 and the graphics are fine. I don't know if it's a GPU driver issue or something else.
- Computer: Dell Precision 380 tower (desktop)
- GPU: Nvidia NV42GL Quadro FX 3450/4000
- Graphics driver: Nouveau
