I run Manjaro on an ASUS UM462 R5 WITH RYZEN 5 3500U and no drivers in the kernel for RYZEN GPU Vega. I am on Kernel 5.6 and have issues with screen rotation (no driver for sensors accelerometer); no graphics processing on GPU.
I have read that AMD is only be included in the Kernel v 5.7 to be launched at end of 2020 maybe(?)
AMD pull your weight on the market and issue all the necessary linux drivers for these CPUs. It has taken since 2018 to get the code from AMD into kernels.