It was available for some days last year from
http://arace.tech - but it was not explicitly listed IIRC and the product page you found using the search function showed it as pre-order only as you mention.
Nevertheless, I got lucky and was able to order one last year. It's a nice device, but software support outside of the provided Bianbu Linux (a Chinese Ubuntu derivative) is nonexistent and the future of the SpacemiT SoCs is not exactly clear. I can run Ubuntu for the BananaPi F3 (same SoC) from an SD card with working drivers and power management but did not yet succeed in installing Ubuntu on an internal PCIe/NVME SSD I added.