@virgiliomi:
@marjohn56:
You might be able to get away with trying managed only on dhcpv6, set up a static assignment for his device, then add a firewall rule to block that address from the internet…
Worth a try...
This is probably the best solution… and should work as long as the prefix from your ISP doesn't change.
One slight issue, pretty sure some or all Android devices won't play though as they rely on on SLAC, but that's not a showstopper, they will still run on v4.