For more technical implementation details, you can refer to the official documentation on MDN Web Docs. Sec-CH-UA-Mobile header - HTTP - MDN Web Docs
The header sec-ch-ua-mobile: ?0 is a that tells a web server the request is coming from a desktop device . sec,ch,ua,mobile:,?0
The ?0 value is a boolean indicator where 0 means "false" (not a mobile device). If you are "drafting proper content" based on this header, your server-side logic should prioritize and features. Content Strategy for ?0 (Desktop) For more technical implementation details, you can refer