BigDi

I tried it with a desktop PC, but couldn't select a resolution higher than 1024x768. I read that there's a bug in newer kernel versions that's already been fixed. However, I couldn't find out if the fix is included in the downloaded image. Then I tried an older imager with kernel 4.4, and with that one, I was able to select higher resolutions. @jock I only tested it with Wi-Fi. You could also try a version with an older kernel.

The Nanopi M4 (not V2) has only 2GB of RAM. It could also possible that my device has an other (or older) Android. And you have to use the HDMI port 1 in the "middle". Not the HDMI under the TF slot!

I tried Armbian_26.2.1_Nanopim4v2_trixie_current_6.18.8_minimal.img.xz, wrote it on TF card and it booted into Linux without any changes.

Which DTB did you use? I extracted the Android files and found a resource file named ENTRrk-kernel.dtb. The file began with "Rockchip RK3399 Excavator Board edp (Android)". Could it be possible that the device is compatible with this board?

I own the same box. Do you unbrick your box in the meanwhile?