Hello ,

i don't know if this is the correct place to state this,
but i have a Desktop PC running 

Ubuntu 16.04 

and i noticed too that the system won't resume from suspend after installation
of 

amdgpu-driver of rx560

this happens with the AMD Driver for 16.04 Xenial

https://www.amd.com/en/support/kb/release-notes/rn-prorad-lin-amdgpupro

but also with the AMDGPU.PRO driver for 18.04

https://www.amd.com/pl/support/1881

I have to say that i use Kubuntu instead of Ubuntu.

 4.10.0-28-generic #32~16.04.2-Ubuntu SMP Thu Jul 20 10:19:48 UTC 2017 x86_64
x86_64 x86_64 GNU/Linux

The System is

Ryzen 5 2600
AMD RX560 2GB
16 GB RAM.

Withouth the AMDGPU Driver there is no problem with suspend as it seems.