If you read the Lubuntu release notes (https://lubuntu.me/focal-2-released/) you'll have discovered
"Note, due to the extensive changes required for the shift in desktop environments, the Lubuntu team does not support upgrading from 18.04 or below to any greater release. Doing so will result in a broken system. If you are on 18.04 or below and would like to upgrade, please do a fresh install." Issues were expected which is why the upgrade path is not supported. I've thus marked this bug as invalid (your system is unsupported). If you believe I'm in error, please leave a comment explaining why and the status can be changed back to new, however a confirmation of the bug report will be required on a fresh install (or install of Lubuntu 18.10 or later which can be upgraded to 20.04) before the issue will be looked at by the Lubuntu team. It may also be your issue is a kernel issue (what your video reminded me of), but this comment deals only with `pcmanfm-qt` or Lubuntu package(s). ** Changed in: pcmanfm-qt (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1961048 Title: pcmanfm-qt ugly dithering on mouseover highlights To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/pcmanfm-qt/+bug/1961048/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs