Like this reviewer says, just replace your old Apple TV with the new Chromecast with Google TV. Unlike earlier models, this Chromecast has a voice remote and a full on-screen UI that runs Android TV apps inside a new content aggregation system called Google TV. So while you still have the option of casting to it from other devices, you don't have to.
If you're missing YouTube, HBO Max, Disney+ and other streaming services that you lost on your third-gen Apple TV, a $50 Chromecast with Google TV is a much more affordable investment than an Apple TV 4K streaming box.
www.macworld.com
IMO, it's the best streamer you can get for $50. I have an Apple TV 4K and love it but it's an expensive device. Bought my parents the new Chromecast as a Christmas gift and it's pretty nice. It even runs the Apple TV app now. Doesn't have other Apple apps, though, like Apple Music or Arcade. If you need those on your TV, you'll need the Apple TV HD or 4K.