I wonder how often the assigned prefix changes with most of the regular ISPs. I'd have to look someone else's router since I'm still stuck on an old contract. But I believe what I saw with some of the regular consumer contracts: the prefixes stay the same for a long time. You could just slap a free DynDNS service on top and be done with it.

But yes, I think this used to be the promise... We'd all get IPv6 and a lot of gadgets like NAS systems, video cameras and a wifi kettle and they'd be accessible from outside. Instead of that we use big capitalist cloud services and all the data from the internet of things devices has some stopover in the China cloud.

My dynamic IPv6 prefix hasn't changed in a couple of years. It only changed because I reset the router config and that changed my DUID. That's good enough for everything I host. I don't even bother with dynamic DNS anymore.

I wouldn't bother with trying to host an email server from a residential connection though. Even if you can get your ISP to open port 25 for you, many email servers won't accept mail from residential IP addresses.

IPv6 costs money to implement so it doesn't happen without good reason.

For ISPs you need many options so that one company can't take all the business. In my area competition is steep so fiber is cheap. In rural areas I'm personally interested in community or small ISPs. Surely some people could get together and make something better.