PINE64 now has stock of the Quartz64 Model B, a single-board computer powered by a Rockchip RK3566 chipset. Currently, the Quartz64 Model B only ships with 4 GB of RAM and also lacks built-in storage, although eMMC and microSD card expansion is available.
https://www.notebookcheck.net/Quartz64-Model-B-PINE64-finally-makes-its-SBC-orderable-with-4-GB-of-RAM.625794.0.html