Wayland with the non-free driver stopped working for me a while ago.
Both KDE Plasma and Weston crash when I start their Wayland sessions,
either from SDDM or manually, by running either `startplasma-wayland` or
`weston` on a TTY.

I'm attaching the logs below. The most interesting parts seem to be:

KDE Plasma:
---
kwin_wayland_drm: Could not create gbm surface! Nie zaimplementowana funkcja
kwin_wayland_drm: Could not create gbm surface! Nie zaimplementowana funkcja
kwin_wayland_drm: Creating GBM surface failed: Nie zaimplementowana funkcja
---

Weston:
---
[12:47:53.887] failed to create egl surface
[12:47:53.887] failed to create gl renderer output state
[12:47:53.887] Failed to init output gl state
[12:47:53.887] Enabling output "DVI-I-1" failed.
[12:47:53.887] Error: cannot enable output 'DVI-I-1' without heads.
---

I'm no expert on this, but it seems to be the same thing for both, just
worded differently. "Nie zaimplementowana funkcja" means "Feature
not implemented" in Polish (I did set `LANG=C`, but the error still
printed in my default locale).

I'm using a Nvidia GTX 660 card.