@ewww Seems that you want to take the nightmare of playing with dts files. So this is your first exercise.
rk3566-box-demo_rboxr2_5.dtb reports that your ethernet is based in RTL8211F but doesnt work. Because we can guess that kernel identification is good, maybe the timing is wrong in 4.19 dts file. Apply the corect timing ( TX delay RX delay) to the board.