I have an old Chinese android tv box mecool km9. It doesn't work as expected because couple of years back google didnt add it to certified box. Also it stops responding often and the last software update by provider was back in 2018.
I use it for youtube (watch from chrome) and Tubi app, sometimes read pdf files. Is there a way I can improve it? Installation a newer OS on it myself or I should buy a new android box. I think the hardware specs are good, it has 4 gb of ram and 64gb storage.
You aren't getting certification on this box whatever you do, but there are pretty great custom firmwares, including ugoos port (that's the best Android box firmware you can get outside Shields) and vortex. Your choices are to embrace piracy in custom firmware or buy a certified box. In any case install STN, stock youtube is dog and pony show.
Here's a good place to start - it's in Russian' but google translate is your friend: https://4pda.to/forum/index.php?showtopic=930374
The best android tv box i have used, is XIAOMI MI TV box.
When i bougth it it was So Cheap i did not ever expect that much of it. But the little box really surprised me in a Great way. I liked that it autoadjusted my picture to best i have ever seen it. And the same goes for the sound the best ihave had on my TV.So if you want to buy, i would really recommend it
Here is my video on a different firmware for your device. Firmware in the link.
https://www.youtube.com/watch?v=_f18R-zqS64