I can confirm this with lenovo laptop t450s kernel 4.4 Kubuntu Xenial i guess relation to https://bugs.kde.org/show_bug.cgi?id=360766 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1555078 basicly this stops external displays come up after resume but for magic if not login after resume and wait time to set brightness auto as configured, some i.e mouse action does wake up external displays. Speculation the drm resume code is broken.....