AMD has posted Linux kernel patches for Navi 14 even though the GPU is yet to be officially announced. The company has also updated the Mesa graphics library 19.2 with support for Navi 10 GPUs such as the Radeon RX 5700 and 5700 XT. Vulkan support is yet to arrive for Navi on Linux so we are likely to see only OpenGL Linux benchmarks on launch day.
https://www.notebookcheck.net/AMD-posts-Linux-kernel-patches-for-Navi-14-GPUs-Navi-10-will-see-only-OpenGL-benchmarks-on-launch-day.426988.0.html