This must be a setting in Firefox somewhere relating to Tabs, so I will continue to investigate, but... I feel like I could always click an email link I had received and it would open my preferred browser, in my case Firefox Mac OS latest (both) on a last Intel Macbook Pro. Now, a link click opens Firefox but only to the last page I was on, and I again need to click the email link to get the new tab to open. Why/where/help please?!