I work at a decent-sized ISP in Sweden, and we've been trying to get IPv6 to customers for over 10 years. It's hard. The way the Internet is built (many municipal broadband networks[0]) means there's middle networks that might not support IPv6 (the reason used to be "no interest" and "it's not a priority").
PTS is starting to show some interest[1], we'll see what leads to.
That's kind of what I'm hinting at, the municipal entities assigned to handle the installation of fiber started this 20 years ago, which means that even 1Gbit is not the norm, the old 100Mbit connections are. I know a person that works at such a place and they have zero interest in upgrading their routers, because it would only cost money for the labour and equipment.