Why a zoo of distributions with different features?

[Arwen]

<snarky>Because we like animals?</snarky>

You are right, we are getting close to mainline kernel support, 5.4. But, in the mean time we are using an older kernel, 4.4.x, probably the latest when Rockchip wrote or updated thier driver's for the RK3399. It has to be installed in to the distro, and we have several people willing to do that intigration work.