Environment:
Ubuntu 18.04 w/ kernel 5.3.1
OpenGL version string: 4.5 (Compatibility Profile) Mesa 19.3.0-devel (git-ffb0d3a 2019-09-29 bionic-oibaf-ppa)
No Radeon Pro drivers installed
Asrock 5700 XT Taichi
2 monitors on HDMI, 2 monitors on displayport

When monitors are only connected via HDMI, monitor power-off on idle works properly. When ANY are connected via displayport or only via displayport, then it appears to power off, but then all monitors power back on.

On a thread on the AMD forum on Reddit, others appeared to have similar issues. Can others report their observations?