I'm running Armbian_20.05.1_Arm-64_buster_current_5.6.2_20200408.img on a X96 Max Plus 4GB, I modified those sections which you changed in the dts file, ethernet is working now, but only 100Mbps. If using the original meson-sm1-sei610.dtb file, I can see through my router that LAN is connected on 1Gbps, but no IP address is issued.
Any suggestion to make ethernet working on 1Gbps?