I can't mount the SD card to do the modification...
It says the GPT table is corrupt. Well that may explains why belenaEtcher throws an error. I used USBImage instead, it doesn't throw an error but the main GPT table is still corrupt.
I have tested with 2 different SD cards.
I believe there is a problem with these Trixie (Desktop) images for Rock 5b+.
(Yes I have checked the checksum after the download)
I'm currently downloading the older bookworm image to check if it works, and that there is no hardware issue.