Thank you for yours!
The situation is mysterious. But I have a new hunch. Could you confirm the following theory:
Your unit boots realiably if an sd-card is inserted. Without an sd-card, your screen remains black.
For example the serial output you collected. Did you collect it when you booted from an sd-card or was no sd-card in your unit when you collected it?
If your unit only boots when an sd-card is inserted, can you try flashing the reform-system-any image instead of the reform-system-rk3588-dsi image and try boot that?
If that does not work, could you try booting from the reform-system-rk3588-dsi image and run the following command:
sudo dd if=/dev/mmcblk0 of=boot.img bs=1048576 count=16
And then upload boot.img somewhere and share it here?