When I was still using Kubuntu 18.10 with Plasma 5.15 (installed from backports repo) the blurry/out-of-focus thing only happens after waking up from sleep. Now, with Kubuntu 19.04 beta, it happens all the time. I also tried this with KDE Neon (user edition) with same results. This doesn’t happen with Nouveau driver or on my laptop with Intel driver.
Here’s a sample video of it. It’s no longer as crazy after enabling flipping, but it still happens frequently enough that it gets annoying.
Operating System: Kubuntu 19.04
KDE Plasma Version: 5.15.4
KDE Frameworks Version: 5.56.0
Qt Version: 5.12.2
Kernel Version: 5.0.0-8-generic
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-6500 CPU @ 3.20GHz
Memory: 15.6 GiB of RAM
GPU: GTX 1060 6GB
nvidia-bug-report.log.gz (1.13 MB)