lucho

Yes, it really is one. It's about 1,5 times wider than the 6 mm diameter outer ring of the 3.5 mm audio jack (that is, about 9 mm wide), so it's USB-C indeed (micro USB is narrower, about 7 mm wide). But as someone here already noted, if one intends to use a Raspberry Pi enclosure and has to cut the lower part of it for the SoC heat sink and the upper part for the USB-C, why not cut the latter a bit more for the barrel jack? The decision to use USB-C for the power supply instead of microUSB is IMHO a halfway one and therefore a bad one, if a 5.5 mm barrel jack can be used instead, which would solve the high power supply current problem much, much better. Hopefully the shown photo is an early prototype and it's not too late for them to fix that.

The problem is not their experience, but the compatibility with the Raspberry Pi that they aim. This reminds me of the dreaded "IBM PC compatibility" which has tortured us for 37 years.

Yes, indeed, it's slightly smaller. But the NanoPi M4 looks like it's not only the same size as the Raspberry Pi 3, but also has the same connectors at the same places. So if it weren't the necessity of a heat sink on the RK3399 on the bottom side, it could be placed in an enclosure made for the Raspberry. But now, to use such enclosure, one has to cut a square hole rotated at 45 degrees for the heat sink. If the connectors are the same and at the same places as on the Raspberry, then the microUSB power connector must be the one that supplies power. IMHO this SBC is too powerful for that.

We're going off-topic here, but could you give some more details? Which SoC will the NanoPi-M4 use? Because there already is an RK3399-based board with the same size as Raspberry Pi 3 – the Rock960.

I think that the hardware development is already complete, unlike the software development, which has only recently started and is progressing quickly (a new pre-release almost every day). As to the hardware revisions, the difference between V1.0 and V2.0 is quite large. The difference between V2.0 and the July 2018 batch is only 1 omitted resistor (R895381), which was probably not needed in the first place. So the bare PCB can be the same as for V2.0. In general, the number of hardware revisions of a product is much lower than the number of software revisions. This is natural. But what's interesting to me is how the price of RockPro64, Orange Pi RK3399, and other RK3399-based boards like the NanoPC T4 can be so low. As many of you probably don't know, the Chinese government subsidises Shenzhen Xunlong Software Company (the maker of the Orange Pi boards), and so they can afford to sell their boards at the BOM (Bill of Materials) cost, not following the "golden rule" that the retail price of a product must be 3 times higher than the BOM cost to pay salaries, depreciation allowances, etc. But their RK3399 board has only 2 GB of DRAM and 16 GB of eMMC flash memory and sells for $109. The 2 GB RockPro64 variant plus 16 GB eMMC sells for even less: just $75. How is this possible? Does the Chinese government subsidise Pine Microsystems as well? Unlikely! Then, what is the secret behind their astonishingly low prices?