Hi @Dominik Wójt, Thank you for your time looking into this. I was really stuck in a loop looking for solutions and this is the conclusion I also came to: The issue is with the kernel, not with DTBs, config, distro, monitor or anything else. I got the output to work on a regular image by installing "linux-image-edge-meson" but still no access to NAND and the device does not run smoothly. Best experience I've had was with an old image with kernel 3.10.108 which had everything working and running smoothly.
I would like to try these patches you mentioned but unfortunately I don't have the knowledge on how to do so, then how to put this into armbian during the build process...
I've now given up on this. Installed LibreELEC with and old kernel and donated the box away. Though I want to thank you again for your suggestions and for your help.