Possibly relevant: https://www.phoronix.com/scan.php?page=news_item&px=Xorg-IGLX-Potential-Bye-Bye
https://askubuntu.com/questions/745135/how-to-enable-indirect-glx-contexts-iglx-in-ubuntu-14-04-lts-with-nvidia-gfx from there: Add to /etc/X11/xorg.conf: Section "ServerFlags" Option "IndirectGLX" "on" EndSection