[p1mrx]

The "single device" problem comes from WiFi, not IP. Normally, you can extend Ethernet by plugging in a switch or bridge, but WiFi is limited to 1 MAC address per associated client, unless operating in WDS mode.

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.

[fanf2]

It isn’t specific to WiFi: there is the same problem if you use SLIP or PPP dial-up or DSL or cellular data, or many kinds of VPN.

And for IPv6 over ethernet, ND proxying is not a protocol you would normally use to construct a network.