Just want to let you guys know that my Nanopi M4V2 runs smooth, cold and hangfree with the latest version. I accidently installed a mainline kernel instead of legacy, but haven't been having any problems since. I can't seem to download this version from the website (there latest is 5.10.12), but you can install this kernel with armbian-config.
Armbian 21.02.2 Buster with Linux 5.10.16-rockchip64
Great work guys!