I don't know if you're the same person who asked on reddit, so I'll copy paste what I said in reply here as I think its worth waiting a bit longer for information regardless of if anyone has tested solus on it or not:
I've confirmed with AMD they do have an open issue surrounding "5.0.9" (the stock kernel of Ubuntu 19.04)
Complicating this issue further is that when trying Linux 5.0/5.1/5.2 kernels on Ubuntu 18.04 LTS, they all booted up fine!
Solus 4 ISO ships with kernel 4.20.16. Once you update you'll be on 5.1.14. I don't know when zen2 support was added to the kernel an there simply isn't enough information on the issue yet to know exactly what is going on. If you're concerned hold off a few weeks to a month.
I plan on waiting at least a week or two, to see if there are any X570 motherboards to steer clear of when paired with a 3900X or are just poor in general. It just doesn't pay to be an early adopter. I've been waiting 7 months with money in my account ready to go for zen2 launch, I feel your pain. I think it worth holding off just a bit longer for.