I'm happy with console=tty0, it works. But next time I hook up the headless board to HDMI, I will also try console=serial.

 

Note that the original was not console=both.

 

It was (at least on my tinkerboard S):  console=ttyS3,115200n8

verbosity=7
fdt_file=rk3288-miniarm.dtb
console=ttyS3,115200n8
rootdev=UUID=24a05491-1fbb-4a44-894d-f3dbef5f721b
rootfstype=ext4
usbstoragequirks=0x2537:0x1066:u,0x2537:0x1068:u

 

There was a change of default to mimick the vendor behavior, that was later partially reverted, I think this is part of that situation. I'll poke at it and provide a separate thread to discuss it and a solution.
@Martinayotte the vendor went from one uart to another between releases, most likely due to blocking a HAT's compatibility.

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