DeletedUser87 Just from a technical standpoint, there's no known way to flash Android TVs. Not to mention that there are most likely no open source builds of the TV's software available anyway.
While specific televisions may be a non-starter (due to the infinite hardware possibilities problem), I suspect that most sane people use an android tv dongle, of which there are many options that are either unlocked or unlockable, such as nvidia shield, ADT-3, or even one of various SBC's like RPi.
And yes, the required source code is most definitely available.
Of course, GrapheneOS's focus on security would be the other big problem, since hardware security is pretty non-existent on such devices. Although.... you could do a TV build for those newer pixels with DisplayPort on the USB-C. They'd make a ridiculously amazing TV box.