There are a whole herd of NanoPi boards now. The M3 uses an 8 core Cortex-A53 SoC, namely the Samsung S5P6818. This board has 1G of DRAM and gigabit ethernet via an RTL8211E chip. Cores can be run at 400 to 1400 Mhz.
They say it will run Debian, Ubuntu, or Android.
The absolute most important thing with boards like this is documentation. There is a 1670 page PDF technical manual on the Samsung SoC, which is encouraging. Next in importance to documentation is source code. Although linux source is so convoluted it is hard to learn anything from it, it can be an almost essential compliment to the hardware manual. Sometimes people working on a linux port have access to inside information or can get questions answered that are not published in the tech manual.
They do have other products based on the S5P6818 SoC, such as the NanoPC T3 Plus, which has 2G of ram, and 16G of eMMC -- and a price of $90 !! More than I want to spend unless I have a real purpose for this thing.
Tom's electronics pages / tom@mmto.org