After investigation, it was probably the boot rom that got corrupted.
On an Armbian image, this was shown on UART.
It seems that, after the TPL loader, boot rom was unable to jump to the SPL loader, which results in the device being stuck.
Something inside the Rockchip SOC must have messed up big time, although I have no idea how it got there.
On an Armbian image, this was shown on UART.
Quote:U-Boot TPL 2020.10-armbian (Aug 08 2021 - 18:02:43)
LPDDR3, 800MHz
BW=32 Col=10 Bk=8 CS0 Row=15 CS1 Row=15 CS=2 Die BW=16 Size=2048MB
Trying to boot from BOOTROM
Returning to boot ROM...
It seems that, after the TPL loader, boot rom was unable to jump to the SPL loader, which results in the device being stuck.
Something inside the Rockchip SOC must have messed up big time, although I have no idea how it got there.