UPDATED: Read comments.
I recently acquired a Radeon VII video card for my Linux box. Sadly, it's been a huge pain in the arse to get working stably. I get hard system lockups when trying to drive my two display port monitors at 1440p @ 144Hz. Interesting enough it's not an instant lockup. First the screen will freeze then I get the screen blinking once to black. After a few seconds I return to the desktop with a complete hard lockup. I must reboot the system via the reset button for it to function again.
I've tried Fedora 30 with updated stock mesa and git mesa from che's copr, RHEL 8.0 with official AMD pro drivers version 19.20, Ubuntu 18.04.2 with official AMD pro drivers version 19.20, and finally Ubuntu 19.10 beta with stock mesa. Every system exhibits the exact same behavior (lock up, black screen, hard lock).
The only information I've found on this subject is a bug report from bugs.freedesktop.org (link below).
Radron VII crash bug on bugs.freedesktop.org
It's seems the problem stems form Linux kernels above version 5.1.0. Sadly, I've had the problem with every kernel since Fedora 30's original 5.0.x release.
The only work around I've found is to run the refresh rate at 120Hz on both monitors (instead of the desired 144Hz). The resolution can remain the native 2560x1440. This setting has provided a little more stable, although still not perfect. I also have to use the Wayland session to get halfway smooth desktop performance. Xorg is choppy and just feels chunky.
On a positive note the Radeon VII simply rocks in OpenGL and Vulkan performance. Every game is beautiful with ultra smooth FPS. As long as I keep the refresh rate below 120Hz, of course. Anything higher results in the above described lockup. Windows games under wine/proton and DXVK are super smooth as are the native games I've tested.
Over all I'm pleased with my Radeon VII card. I am willing to wait for the proper kernel bugs to be hunted down and squished.