If you've got involvement of `lxpanel` (LX Panel), as that's not used by Lubuntu 18.10 upwards, thus I'd recommend re-install as already outlined. Lubuntu last used that program/package in 18.04 and it won't exist on LXQt installs.
When Lubuntu switched from LXDE to LXQt; many used applications were switched from deprecated GTK2/LXDE ones to Qt5/LXQt equivalents. I find the site https://phab.lubuntu.me/w/bugs/ useful for comparison if you're not aware of the changes.. but as that LXDE detail is no longer supported/useful, it should be expected to disappear anytime. My reference to Linux in my prior comment (last paragraph) was referring to the kernel (including kernel modules; eg. radeon etc) as I'd seen the issue in your video before, and your video reminded me of that. However this bug was filed on a LXQt application thus detail provided (at filing) concentrated on that part of the software stack. Your system is unsupported at that level though due to lack of re-install. You could re-file against another package but many such required details currently do not exist on this bug report as filed against user-level application. -- 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
