When I run a Vulkan game such as vkquake or Talos Principle, tearing occurs with enabled KWin compositing. This shouldn't happen, since vsync setting of KWin is set to either always repaint or reuse of image parts. This does only occur with Vulkan applications, OpenGL games are fine (applications are not allowed to block compositing). Doesn't seem to be limited to certain proprietary Nvidia driver versions. As a workaround, the vsync compositing for such applications can be enabled by reenabling it via hotkey (turning it off and on again). I'm on this repo currently (but I think it alo occurs with latest 5.8 stable version): http://download.opensuse.org/repositories/KDE:/Unstable:/Frameworks/openSUSE_Factory/
Tearing in the Vulkan window or in the complete screen? I myself have not been able to run any Vulkan applications yet and our code is not yet adjusted it adjustments are needed
It seems the whole screen is affected. When I run the application windowed and move another window (e.g. normal Dolphin window) on top of it, the window on top tears as well. The tearing also only occurs at the very same position, near to the top of the screen. vkquake is a very compact program which may be helpful for quick tests: https://github.com/Novum/vkQuake
Closing, as it apparently is an issue of the Nvidia driver.