Since QPA only performs off-screen rendering, it does not require an EGLConfig that supports any particular surface type.
Currently it requests a config supporting window surfaces, however the EGLDeviceEXT platform, which is the basis of the
EGLStream back-end used with the proprietary NVIDIA driver, does not support such surfaces resulting in eglChooseConfig
not returning any valid configs when that back-end is in use. Since QPA doesn't actually create any window surfaces, it should
be fine to remove this restriction to allow it to initialize properly with the EGLStream back-end.

Start a Wayland Plasma session on NVIDIA hardware with the proprietary driver (see https://phabricator.kde.org/D18570)
Configure the window switcher to use the breeze theme and trigger it (with alt + tab by default)
KWin should not crash and the window switcher dialogue should be displayed correctly.