Centmin Mod Nginx HTTPS sites with front facing Letsencrypt SSL certificates may have the old longer DST Root CA X3 chain which has expired and on older client devices like Windows XP or Windows 7, the web browser like Chrome might report insecure connections to your sites:...
Windows 2012 R2 An other notice: I have a third website C, running an SSL certificate from Comodo. It's still working well and it's the only website served with a certificate different from the A. It's also the only non letsencrypt website on the server. ...