That's just like me.
I use the Khadas-Edge image with the same DTB file from Recalbox.
Yesterday I tested the test image (is kernel 5.1) of Kwiboo .
It already works fine and under kernel 5.1 the NanoPC-T4 is natively supported, so there is also a DTB file.
You tested the dtb with which image? One from Index of /? Was the Wi-Fi working, because without it I would have no access to it lol