I'm surprised they didn't have it until now. Every cloud provider's load balancer and CDN has had IPv6 for a while. That they don't have it for the site or SSH is less surprising, but GitHub Pages is static content.
Maybe AWS, Azure, and GCP, but not places like Digital Ocean. IPv6 is still very niche, and it's suffering from that effect where it being very niche keeps it very niche. Nobody wants to be an early adopter (and momentum seems to be dying), and the result is that there's no adoption.
I think we've been trying to make IPv6 happen since 1998, and ... it's not happening.
It's absolutely glacial, but IPv6 adoption has been steadily rising over the last 8 or so years. Unfortunately the increase has been linear rather than exponential.
That is, according to Google's stats of clients accessing their properties. Not a perfect snapshot of worldwide Internet users, but a pretty decent one. https://www.google.com/intl/en/ipv6/statistics.html
Even a linear growth is fine. By 2030 there will be pretty much 100% adoption at this pace. There may even be a tipping point when places like India are so stretched for v4 addresses and v6 is so widespread where local sites go v6 only which triggers a much faster adoption rate on the consumer side.
Linode fully supports IPv6 and it works quite nicely.
I used to have a Hurricane Electric IPv6 tunnel but I've abandoned mine as my small rural cable provider turned IPv6 on quietly (all you have to do is have your router ask for a /48).
