My consumer router, and every router I have configured, implicitly supports IPv4 NAT out of the box. But it will never NAT an IPv6 network. If I enable IPv6 then it operates by IPv6 rules, which means each device gets a Network ID and each Network ID gets routed directly and transparently. The router has no NAT table and no NAT settings for this protocol.
So if NAT is “supported” whatever that means, it simply isn’t possible for most end-users.
Consumer routers don't support lots of useful stuff though, so them not supporting NAT66 isn't very surprising. Enthusiasts are likely to use OpenWRT or nftables, both of which support NAT66 [0], and quickly Googling some random enterprise routers shows that they all support NAT66 too [1] [2] [3].
This isn't enabled by default because it's usually a bad idea, but it's certainly possible if you really want. (It's discouraged because NAT in general is a bad idea, but it's no worse with IPv6 than with IPv4; the only difference being that IPv4 effectively requires NAT.)
If you've got a car that can't go 100, that doesn't mean nobody can, or that it doesn't exist. I don't care if you can't do it, it IS supported in the spec.
That’s an interesting analogy because there’s several ways you could easily dismiss it.
For example: if roads aren’t built to support cars travelling at 100 miles per hour then it doesn’t matter how much you argue that cars are can do 100MPH, because you’re still not going to be travelling at 100MPH.
Or
But if the only cars that can travel at 100 MPH are Bugatti Veyrons then it’s safe to say that 100MPH cars isn’t something available to even the average consumer of high end sports cars.
Or
Sure, some cars can travel at 100 MPH, but they’re so unstable at those speeds that it’s not even safe to attempted it.
You say that, but in practice it does not.
My consumer router, and every router I have configured, implicitly supports IPv4 NAT out of the box. But it will never NAT an IPv6 network. If I enable IPv6 then it operates by IPv6 rules, which means each device gets a Network ID and each Network ID gets routed directly and transparently. The router has no NAT table and no NAT settings for this protocol.
So if NAT is “supported” whatever that means, it simply isn’t possible for most end-users.