Currently using a Renoir laptop. It's smoking fast but I had to install a bleeding edge kernel to get the display driver to work at all. That should be fixed in the next ubuntu release though.
5.10.x kernels are very stable and feature complete with AMD Ryzen Renoir - I update one almost weekly once new patch version is out on Ubuntu Kernel PPA. Here is nice script which makes the update trivial: https://github.com/pimlie/ubuntu-mainline-kernel.sh
Weird, I had no issues with the built in display on Ubuntu 20.04, but I had to update the kernel to 5.8 to get display out over USB-C to work. Now that Ubuntu 20.10 is out and uses 5.8, I'm just using that so I don't have to mess with custom, unsigned kernels.
