You can find that information on the security tab of your browser's developer tools. You can also find a lot more info about any site's HTTPS configuration at s

You can find that information on the security tab of your browser's developer tools. You can also find a lot more info about any site's HTTPS configuration at ssllabs.com. Here's the report for lists.gnu.org: https://www.ssllabs.com/ssltest/analyze.html?d=lists.gnu.org https://www.ssllabs.com/ssltest/analyze.html?d=lists.gnu.org