Don’t worry about whether or not the TV “has Dolby Atmos”. Just make sure you purchase a TV equipped with HDMI eARC, and then find a Dolby Atmos source to play through the TV to the Arc.

The LG C1 is equipped with HDMI eARC. You can use its native streaming apps, like Netflix or Disney+, to play Atmos content, or you can connect an external media device to the TV, like an Apple TV 4K or Blu-ray player, and play Dolby Atmos content through the TV to the Arc.

The amplifiers and speakers in a lot of TVs are not as good as separate units such as the Arc. TVs (like most goods) are built to a budget. A good picture is usually a key factor in a tv; sound is of lesser importance. 
 

If you’re happy with how the tv speakers sound, and if you can stream music to it, you don’t need the Arc. 

So there is no way to make the TV DV and the Arc to work together ?

It's such a waist  of good speakers and good surrounding. 

Why would you want to run two sets of speakers? Sonically, they probably sound different. There may also be a small delay between the sound from the tv and from the Arc, which will muddy the sound. But if you really want to, you may be able to run both together, depending on whether the tv speakers are automatically muted when you send to external speakers or whether you can opt to leave them turned on.

I see 

You.might be right about the delay. 

So I see now that a TV with D.V is not important selling point for tv when you have the Arc.

Thanks