IPv6. Lack of IPv4 addresses it's a problem, specially in poorer countries. But still lots of servers and ISPs don't support it natively. And what is worse. Lots of sysadmins don't want to learn it.
My university recently had Internet problems, where the DHCP only leased Out ipv6 addresses. For two days, we could all see which sites implemented ipv6 and which didn't.
Many big corpo sites like GitHub or discord Apperently don't. Small stuff like my personal website or https://suikagame.com do.
Lots of really large sites are horribly misconfigured. I had intermittent issues because one of the edge hosts in Netflix ‘s round robin dns did not do MTU discovery properly.
My isp decided to put me behind a CGNAT and broke my access to my network from outside my network. Wanted to charge me $5 a month to get around it. It's not easy to get around for a layman, but possible. More than anything it just pissed me off that I'd have to pay for something that 1 day ago was free.
Set up a reverse proxy on another machine (like one of those free oracle cloud things). I can't go into detail because I don't know exactly how. I think cloudflare also has options for that for free. Either way it's annoying.
Say this to my very large Canadian ISP who still doesn’t support IPv6 for residential customers. Last I checked, adoption in Canada was still under 50%.
50%?? I fucking wish. In Spain we are at 5%. I finally got IPv6 in my phone this year, but I want it in my home, which is still only available as IPv4 even if they're the same ISP.