Wake from sleep with nvidia-modeset

nvidia-driver-460.84 from ports, nvidia-modeset, NVIDIA Quadro K1100M 
(GK107GLM), HP ZBook 17 G2, KDE Plasma.

<https://bsd-hardware.info/?probe=c7fb9e9dee>

An initial wake from sleep was almost entirely successful, one exception:

* title bars of windows lacked colour.

Since then: all sleeps succeed, however I can never wake the computer. 
There's an (immediate) dimly lit screen but nothing visible, and no 
response to keyboard or trackpad input. It's necessary to force off the 
computer.

I experimented with nvidia-driver-390-390.144, no better.

Any other suggestions?

I'd _love_ it to work, and the one near-success makes me believe that 
it's possible.