An An

You should not advise to buy shit, they are cheaper because:
* they are made of scrap parts, that often break after very short usage (see the emmc in the rk3318 thread)
* they have no kind of warranty
* the power supply is a joke, made of cheap components and very lousy - switching power supplies are one of the thing the more they weight the better; confront with a quality 5V/2A power supply and see the difference
* the HDMI cable is crap quality, often not capable to transfer CEC or collects any kind of interference at 1080p/4K
* the case is a bit of plastic, with little to no design for heat dissipation - right now I have a rk322x board here withing its case that reaches 97°C while simply installing a package with apt...
* many sorts of limitations to keep them as cheap as possible: no sd card UHS mode, no real shutdown/suspend, USB ports have limited power: be prepared to have headaches if you try to attach something that requires just a tiny bit more power like an external hard drive.
* wifi is a lottery and clearly tells you the general quality: you can find freshly made boards with wifi chips discontinued years ago!
 
Most of all: they have absolutely no software support; if you are able to run armbian on your tv boxes it is because some people within armbian and other projects spent their time for the fun of making it.
Tv box makers don't care at all, they just need to sell their cheap shit to make some profit. Some (not all) SBC makers at least in some way provide support, but tv box makers are mostly parasitic and should not be endorsed.
 
Now that you stated that about 20 pcs of different tv boxes run armbian, may I also ask you what you did in change for that for armbian? Because tv box makers obviously did nothing for armbian, still keeping up the servers infrastructure and the general maintenance cost real money to real people, and who pays that?