How to control sound on TV/monitor via Apple TV?

I have run into a stupid problem and I do not know, how to solve it. I am hoping some in here might be able to help me.

I have purchased a computer monitor together with an Apple TV. I thought it would work together as a "TV" - I was looking for a 32" TV-solution in 4K in my summerhouse and hence the wish for a "small" TV.

I thought the Apple TV could control the audio. It turns out it cannot as the monitor does not accept IR-signal. How do I go about this problem?

I have tried to find an "IR USB-stick", but that does not seem to exist. Then I have thought about adding a soundbar, but would that work, if the monitor just has HDMI and no ARC? 

Would the HomePod solve the problem? Would that be controlled directly from the Apple TV?

If I could get a Roon Ready soundbar I could solve another problem and would be tempting.

Any help would be much appreciated. Thanks a ton in advance.

PC monitors don't have any sort of remote control built in, and often don't even have speakers.
To do what you want to do you really need an HDMI capable tv/monitor with coax or optical out. That assumes you have some sort of preamp or integrated with coax/optical in. Another way is to put an HDMI audio capable integrated or receiver between the Atv and the monitor. The best way if you simply want sound from your "monitor" is to buy an HDMI capable one with speakers. Done. Ultimately you need HDMI-HDMI compatibility. There are various converters and such, but then you just get needless cables etc and not the best overall solution. You can program your Atv remote to run all of the above setups to some degree. My Atv remote controls volume on my preamp, but doesn't do anything else. It is more capable with my tv, but not much.