Not sure what you mean with “classic hdmi”.

Two questions:

• does your TV have HDMI-ARC?
• how do you plan on using you TV, with built in apps or external sources?

The Arc needs HDMI-ARC to be able to play (compressed) Atmos from built in apps on your TV - it depends on your TV if your TV is actually able to do this. If you want to use external sources for full Atmos you need HDMI-eARC.

yes my TV is equipped with HDMI arc, so is this enough? does the signal go through this source? and therefore it is not necessary that this technology is native to TV ?! in fact I use it to watch movies on Netflix for example

Nobody can say if your TV is able to play Atmos on an Arc, unless they have tried with the same model.

What specific model is your TV? Are you using a Blu-ray player? Are you streaming from native apps on your TV or apps from an external streaming device like a Roku or Apple TV? If you list your full setup, we can assist you better.

the model of my TV is a Philips 65PUS6703 / 12 and at the moment I do not have a Blu-ray player yet and mainly the main source is Netflix or Raku, I would like to understand if the Dolby atmos signal must be native starting from the TV or it is necessary to have HDMI arc? and then simply the encoding of the atmos signal starts from sources such as Netflix etc? regardless of the TV model

It starts with the source being encoded with Atmos audio. Whether or not your particular TV supports playing Atmos audio from that source is the question.

According to the manual, your TV is equipped with HDMI ARC and supports Dolby Digital Plus which is the audio codec that carries Dolby Atmos audio when streaming. But the question is whether or not your TV can play Dolby Atmos from any of its native apps or can pass through Dolby Atmos from an external device like a Roku. The only way of knowing this is to test it or find another Phillips 6703 owner who has.