I tried to run Armbian on MVR9 with different dtb files. The test system runs with almost all options rk3328*. When using the (rk3328-evb.dtb) option, the system is very slow. The dtb at a different part of the iron does not work (this is understandable). Therefore, those who try to start the system on their TV boxes, I recommend manually check all options dtb (copy in turn to the root FAT and rename to "dtb.img " all options rk3328*). Perhaps you will find one that will work better than others.
During the test I found out (for myself) that on MVR9 the boot block from eMMC is started first and then it tries to start the secondary boot loader either from SD card or, if it does not find it there, from eMMC (on other TV boxes it is possible it is differently). On V88, I see the same algorithm. So there is a chance to use a universal image and only change the secondary loader to run on different models of TV boxes.