We're pretty much ready to cut our ridiculously expensive cable channel subscription through Xfinity and go with another option (most likely Hulu).

BUT

We've used an apple TV (those black boxes that look like hockey pucks) for years in order to stream shows that are available on the internet to our TV. Our set up is a mac desktop -> screen mirroring > Gen 4 apple TV hockey puck attached to our (old, dumb) Sony TV via HDMI cord.

All worked just fine and dandy until this week when we upgraded to whatever the current version of Monterey is. Suddenly we are having all sorts of weird issues, regardless of browser or streaming service.

1. We can see everything just fine on the TV. As soon as we start to mirror to the apple TV one or more of these things happen

2. We get a black box that plops on top of the show we're trying to watch, so we can only see a part of the show. Audio is fine.

3. We get audio just fine, but the streamed show screen on the computer is totally black. When you put your cursor in the lower right, you can "see" that there is video in picture-in-picture, but no way to expand it (or turn PIP off).

4. When I'm not streaming at all, the mirroring from the mac to the TV works just fine.

5. Apple TV+ (the app, that shows only their stuff) works just fine.

I can't find anything on the internet to help. Then again, I'm also struggling with a good search string... "weird black box pops up when streaming TV using screen mirroring to an apple TV...." ugh.

Has anyone encountered this, or have any ideas what might be going on? And before you answer, yes we have:

rebooted the router and modem
rebooted the computer
cleared various caches on all the browsers
rebooted the hockey puck
checked for firmware

Is there some way to check what the output resolution is on the screen mirroring to see if it's compatible with your TV? I wonder if that setting somehow got overridden during the operating system update and now the TV can't recognize the input it's getting.

Total wild ass guess on my part....

Is it possible to reset the Apple dongle and set it up again?

Since the problem started with Monterey. Check for an update that corrects it.
Why do you need a computer in the setup?
A splitter could add new HDMI connections. I use one to add a Roku to Bob's old Panasonic. I get Apple, Prime, and Netflix plus Youtube and other free streamers through Roku.

I’m not familiar with the Apple setup, but it sounds like all it does is let you mirror from the laptop to the TV. If that’s the case I’d look in to installing Roku sticks instead.

I have several of them and I’m very pleased with how well they work. All of the streaming services are built right in and the Roku remote also controls TV on/off and volume. They also support Apple screen mirroring. No laptop required.

FWIW, I like the way the 4K Express + version installs better than the other models. $35.