So an unprivileged WiFi client needs to hide tethered devices and VMs behind a single MAC address, using ARP proxy (IPv4) or ND proxy (IPv6). These proxies do NAT-like mangling of MAC addresses, but are mostly transparent at the IP layer.
The Linux environment on Chrome OS uses ND proxy, and IPv6 works fine on WiFi. Compare that to WSL2 on Windows, which is IPv4-only.
And for IPv6 over ethernet, ND proxying is not a protocol you would normally use to construct a network.
This is probably why going to v6 is so confusing even for us Elite HN Readers; you don't have a private network connected to The Internet any more, The Internet directly extends to all devices. You can have a private network _in addition_ to that though.
This is actually pretty nice because it restores end-to-end connectivity, so P2P and mesh networking become easier; however, most everyone has a central firewall between their splinter of The Internet and The Greater Internet, so in practice you still need hole punching and some central services to offer hole punching duties, because hole punching works around NAT and opens a port in stateful firewalls; v6 only removes the NAT part in most instances. So in reality P2P with v6 is only slightly less messy than with v4.
ULA seems to be RFC 4193 (October 2005). NTPv6 is RFC 6296 (June 2011).
One of the vexing things about IPv4 (which is not really fixed by IPv6) is that endpoint devices are connected to the network but not really part of the network: there are different sets of protocols for connectivity within the network, and at the edge of the network. So an edge device (your phone, your VM host) can’t easily extend the network to more downstream systems (tethered devices, VMs) without hacks that hide the cluster from the network so the whole thing still appears to be a single device.