If you go to
Help > ChaptGPT Atlas Help
it'll link you to some docs[1] and under "Setting up the Atlas browser"[2] it opens with
> Atlas is OpenAI’s Mac browser built on Chromium.
If that counts for anything.
[1] https://help.openai.com/en/collections/16051538-chatgpt-atla...
[2] https://help.openai.com/en/articles/12628461-setting-up-the-...