alt Hacker NewsGitHub is the main problem currently. Some software like composer does not work due to this.
https://github.com/orgs/community/discussions/10539
For countries, if you meaning connecting to VPS, lot of countries have good IPv6 connectivity now. For me both ISPs I use have native v6. This will differ from person to person.
It is inconcievably stupid that github, run by a massive tech company like Microsoft, has not migrated to ipv6. They're single-handedly holding back adoption.