Rebooting the gateway has fixed it.
@daedalus Huh. IPv6 wasn't working for me either. Restarted the dhcp6 client, no joy. Restarted gateway, all good.
Starting to come around to the battlestar galactica view of computer networks.
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!