"homegrown"

"based on the existing open-source Linux operating system"

[1] suggests it's a distribution that isn't directly based off another distribution.

[1] https://news.itsfoss.com/openkylin-linux-os/

Wasn't Red Flag Linux [1] their first?

[1] - https://en.wikipedia.org/wiki/Red_Flag_Linux

I'd guess it is the first independent linux distro, with its own Desktop Environment, Installer etc. Which is seemingly completely independent from things outside of China, well except the Kernel and that it preinstalls Firefox as a browser.