$ curl -s -I 'https://www.sfgate.com/' -H 'User-Agent: curl/7.54.1' | head -1
HTTP/2 403
$curl -s -I 'https://www.sfgate.com/' -H 'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/113.0' | head -1
HTTP/2 200
One "trick" is that Firefox (and I assume Chrome?) allow you to copy a request as curl - then you can just see if that works in the terminal, and if it does you can binary search for the required headers.
