Arvo

If all other things work well (except for ethernet) then your used image is OK and you can play around with dtb configuration. Cheap TV boxes are made from available parts, which means lot of hardware variations. You can try to use different dtb files (one at time) and if you are lucky, you will get fully functional and stable Armbian device. Even if you find a dtb, which provides ethernet w/o WiFi (or w/o some other functionality), you are also lucky, because Frankenstein dtb can be crafted from both Don't forget to check sensors under load (apt install lm-sensors), as TV box CPU radiators often are small, cases has no ventilation holes and CPU settings of used image may be not optimal. Once I did similar exercise with Tanix TX9S and was lucky (even bluetooth started), so good luck to you as well.

I tried recovery menu approach with Tanix Tx9 - no success via boot and also same through upgrade from Armbian config app. Recovery button method worked out, although afterwards had to play around with dtb files. May be this switch is soldered on board (or contacts intentionally left visible with some marking) to be accessible after some disassembly .