Comment 9 for bug 2063503

I added the following line to /usr/src/linux-headers-6.8.0-36/include/drm/drm_ioctl.h (line 34)

#define DRM_UNLOCKED 0

And then I installed ("sudo ubuntu-drivers install") & it worked.

If it complains it's already installed, you might have to first remove the partially-installed nvidia software:

sudo apt remove $(dpkg -l | grep -i nvidia | awk '{print $2}')