The wiki page at:

https://www.funtoo.org/Create_a_boot_option_for_easy_nvidia_or_nouveau_display_driver_switching

needs updating due to the new graphics stack that uses libglvnd.

All graphics drivers must be blacklisted and kernel  options  (such as nomodeset) that trigger drm should not be used.{{ drm should be delayed until init function xcfgmaker is started. The files at /etc/modprobe.d/blacklist.conf and /etc/init.d/xcfgmaker are attached and worked for me but need to be checked.}}