Is there some kind of "alternative OS" for this Game Tv stick?

[Xdqwerty]

Like the sup m3 having miyoo cfw as an alt OS.

 

[Hayato213]

Probably not.

 

[hippy dave]

It's Android, so you can customise it in all the ways you can customise any Android installation (apps, rooting, configuration tweaks, Magisk/Xposed). The closest thing to "custom OS" would be if anyone has built custom ROMs for it (which are customised Android builds) - xda-developers.com would be the first place to look, depends if anyone has taken an interest in that particular device.