I just installed Android TV[1] on my Raspberry Pi 4 just 2 days ago. This will give you the same error because it is not authorized by Google (known issue!). Apart from that everything else runs fine on the Pi. I would however not recommend it as my Pi sometimes freezes when interacting with the menus. But streaming from ie. Max for a couple of hours works without a hitch.

Because I tested casting to the Pi and got that error and then suddenly getting the same error on my official 2nd gen stick I got very paranoid and spent a couple of hours troubleshooting sigh.

If it is a botched firmware update - or simply someone at Google messing up the current signatures - it is not a good look for them.

But I guess it is again only us techies who really cares how easily they remote bricked our devices. From the reports and the sniffed network traffic I lean towards messed up keys rather than botched firmare update. All hail our digital overlords.

Made me think of what my real practical alternatives are. Unless I want to fiddle around with a browser while lounging on my couch it seems the only other real game in town is Apple TV. We have locked ourselves into the walled gardens. The powers that be never really understood that it was not fierce control but rather human nature and convenience which won the war against piracy.

[1] https://konstakang.com/devices/rpi4/LineageOS22-ATV/