There are many Linux Users at AMD Forums. Possible one of them may be able to answer your question.
But you can try at this AMD Linux Forum. Probably have a better chance of getting an answer: https://www.phoronix.com/forums/forum/linux-graphics-x-org-drivers/amd-linux
Just use the default drivers that come with Ubuntu 18.04.01 unless you need the AMD 18.30 all open drivers for a particular reason.
You will save yourself installation headaches.
I would like to use default drivers. But for my card rx 560 amd drivers are more stable, than default drivers.
With default drivers sometimes I have screen artefacts and glitches. But amd drivers are "slower" in 3d applications.
I have found that the default drivers in Ubuntu 16.04 LTS or latest Fedora are really good for gaming on Linux.
The only problem I had was Vulkan games like Doom would not run on the default Drivers. In that case I installed the "all open" amdgpu drivers.
I tested Steam Play Beta with the latest drfault drivers in Fedora recently.
I will point you to the link ...