Noticed that GitHub Pages gained support for HTTPS over customer domains. Actually quite a few months ago.
Adding HTTPS was a breeze. I just needed to update my DNS editor with four new IP address found here.
Wait five minutes for your newly configured DNS settings to spread around the Internet. Then reconfirm the DNS configuration with below command in the terminal window.
dig wramdemark.se +nostats +nocomments +nocmd
The above mentioned IP addresses should appear. After that I went into the Settings page on my GitHub Pages repository and re-added the custom domain. Voila, HTTPS spot on.
GitHub Pages are working together with the great organization Let’s Encrypt who is working for securing the Internet. I have already used Let’s Encrypt in other projects, for instance when running my home automation system, Home Assistant.