Take a look to this OpenWrt 22.03-rc6 "Build" for TV-boxes (rk322x) - #16 by Wyk72
And of course ARMBian.
Of course is a good idea if you use the STB only for captive portal, i.e: two stb, one as wifi controller, and one as STB to play videos and so on.
But if you want to use the STB as STB with Android, it must be a real hard thing and hard to implement, I thing it's not worth the endeavor. It's better one device for captive portal, and another one as STB.