While it's not the same as what you're asking for, you could do this pretty easily with a Raspberry Pi. That feels like such an obvious thing to say that I hes

While it's not the same as what you're asking for, you could do this pretty easily with a Raspberry Pi. That feels like such an obvious thing to say that I hesitated even saying it, but then I started thinking about how funny it is. A solution to HDMI being so locked down is to buy a $20-ish computer, that does all the things a computer can do, so that we can feed the TV the video stream we want. Over HDMI. Given that it's so easy to circumvent now, I wonder why anyone even bothers with HDMI any more, aside from inertia.