After updating to nvidia-drivers-169.09-r1 libwfb.so is missing. Instead libnvidia-wfb.so.169.09 is installed.
The nvidia-drivers-169.09.ebuild had installed the libnvidia-wfb.so.169.09 as libwfb.so.
If the wfb lib should be installed with his original name, then either the eselect-opengl package must be updated to handle this, or the nvidia ebuild generates a symlink named libwfb.so.
*** This bug has been marked as a duplicate of bug 202978 ***
Created attachment 143765 [details, diff]
adds symlink generation for libwfb.so to the nvidia-drivers-169.09 ebuild
ebuild-patch which adds generation of the libwfb.so symlink to libnvidia-wfb.so.169.09