OpenWRT stable build 21.02 is now available for the R2S.
https://firmware-selector.openwrt.org/?version=21.02.0&target=rockchip%2Farmv8&id=friendlyarm_nanopi-r2s

This version includes Luci and ran on my hardware just fine.
Here is a video of the a speed test on this version.
https://youtu.be/leEENEXIuGI