As a follow up: got my board yesterday. 2GB RAM as announced, no obvious bringup probs. The Ubuntu image runs from SD, UART ok, got 80mb/s from SD and around ~300mb/s from an 128GB 2230 NVME. No boot from upper m.2, only lower m.2 boots (works as announced). The SBC starts via uboot stored on the 16mbyte SPI flash, so I think it should be possible to also boot from upper m.2 since the uboot recognizes media both m.2 slots. Currently unclear how to recover from damaged SPI flash, so I need to proceed carefully. Uboot env is closed (bootdelay=0), so first task is to open up uboot cmd line. Theres a boot switch that seems to trigger some USB boot from ROM but thats undocumented AFAICT. Plenty to investigate for my 50 bucks 😉

What kernel version are you using?

Updade: i tried to flash to memory using a male to male USB "Bus 003 Device 008: ID 1f3a:efe8 Allwinner Technology sunxi SoC OTG connector in FEL/flashing mode" Needless to say, i've been duped, scammed, fooled perhaps. I found a picture of a model exactly the same as that one, and it had a H3 chip, since from what i see Rockchip is best supported by the comunity, i'll give up on this board. Tomorrow i'll do one last update when the USB-TTL arrives, to see if my suspicions are confirmed.

Can you get an orange pi zero 3? As a hardware beginner, you need a very stable, well known linux board.

Sorry, I've never done anything like this before. I tried setting it up according to instructions in various GitHub threads, but it always failed. You're the only person who helps me with advice, and thanks to you, I've only been able to build an image with the required kernel module. I haven't achieved anything else, except for the white screen.