If we wanted what other countries have for internet, then what we need is to make the lines public and have ISPs rent them from the government. The reason ISPs can create these duopolies is because every new company has to invest a LOT of money to lay down new data lines. If a company already has their cable/phone lines in place then boom, captured market.
Rentable public data lines would make the cost of setting up new ISPs a LOT cheaper.
All of my neighboring blocks have 1g/1g from them, but the most they offer at my address is a 40/40 "fiber-based coax" internet that I'm probably not even wired for. I would love for that to change - my DOCSIS internet has been pretty solid, but I miss the gigabit upload.
Wave G (NOT Wave's coax-based DOCSIS that they bought years ago) offers/offered IPv6 via PD, lots of documentation for it around the internet: https://gist.github.com/dmtucker/cf3f241cf002367825633c988ff... (this isn't me).
I haven't been a Wave G customer in a number of years, but I don't anticipate it's changed since ~2018
Anecdotally, I moved into a newish (~5 year old) apartment building in Seattle and had my choice of three ISPs that each provided symmetrical gigabit for around $60/month, delivered via an Ethernet jack in a low-voltage cabinet in my closet.
Getting it wired up took one phone call, wherein my switch port was activated remotely and I could grab an IP address and start using the internet. IPv6 via DHCPv6-PD and everything else worked without a charm.
On the other hand, where I live in (also Seattle) is served by exactly one ISP via DOCSIS, providing 1000/35 but nothing more. It can vary block by block here unfortunately.