The subscribe buttons don’t do anything (top right corner and bottom of page). I have checked for javascript errors in the console but don’t see anything relevant.
Yes, I understand, but why is it happening. Does this mean there is an error in the template? Do I need to find the places in the template where it is using http and change it to https?
In this case, your Ghost config has the URL as http://blog.linuxdeveloper.io/ instead of https://blog.linuxdeveloper.io/. All URLs generated by Ghost will use the URL you configured there which is why you’re seeing the issue.
To fix this, run ghost config set url https://blog.linuxdeveloper.io/ in your ghost installation directory, and then restart ghost with ghost restart.