According to this bug: https://bugs.kde.org/show_bug.cgi?id=382812 the issue is not plasma-workspace, nor sddm, nor nvidia, but xorg and according to it the bug has been fixed in xorg. Closing now, if the bug still persists please reopen with details on a supported release.
** No longer affects: nvidia-graphics-drivers-375 (Ubuntu) ** No longer affects: nvidia-graphics-drivers-384 (Ubuntu) ** Bug watch added: KDE Bug Tracking System #382812 https://bugs.kde.org/show_bug.cgi?id=382812 ** Changed in: plasma-workspace (Ubuntu) Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1684240 Title: Lagging square around mouse pointer To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/plasma-workspace/+bug/1684240/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs