I don’t understand the hows and whys. A series I watched on TNT played commercial free when I streamed it by browser. If I watched it through the provider set-top box, it has commercials. Some networks, it doesn’t matter, you get adverts regardless of method.
The TV/Internet provider I have participates in something called TV2GO. There is a list of networks that are available this way. To view TNT, I go to the TNT site list of the episodes. Click “sign in” with the provided box, then get sent over to the TV provider’s site for credentialing. TV provider sends an auth token back to TNT, then video reloads commercial free and in full. Stream that to a device (Chromecast, etc.), and it’s great.
I don’t understand the dropping of adverts, nice as it is.
On Linux computers, a good browser choice for casting to a device is the Vivaldi one. Even though it’s based on the Chromium browser, it avoids me having to install Google Chrome, or Chromium.