05-05-2019 07:02 AM
I am pleased to report that after upgrading my X1E (4K, 8750) from Ubuntu 18.10 to 19.04, sleep/wake has worked every time!
With 18.10, the machine would appear to sleep (ie suspend) - the screen would go dark and the power lights would slowly fade on and off. But it would fail to wake properly - I had to cycle the power and reboot. I would always be jealous of the Pop!-OS users who had sleep/wake long ago.
But the upgrade to 19.04 brought sleep/wake to Ubuntu too, even with two external displays: a 4K on the USB-C/DisplayPort, and a HD on HDMI.