I don't think EUI-64 being built into link-local fe80 addresses is a privacy issue. Link-local addresses don't get routed, so nothing outside of that network w

I don't think EUI-64 being built into link-local fe80 addresses is a privacy issue. Link-local addresses don't get routed, so nothing outside of that network will see or know about them. As far as the router itself, e.g. your ISPs router, it can already gather MAC addresses if it wanted to, so IPv6 using the MAC to generate link-local addresses doesn't add or remove to that situation. CGNAT is not the Internet working well. CGNAT makes you have to have your ISPs permission and coordination to originate outgoing traffic--imagine if you had to ask the power company for permission to operate each electrical device in your house.