Depot CI now supports link-local IPv6

You can now enable link-local IPv6 addresses for Depot CI VMs. This is useful for Docker network tests and services that bind to IPv6.

Note that Depot CI VMs are not globally IPv6 routable; the addresses are link-local only.

IPv6 is off by default. Organization owners can turn it on from the Depot CI sandbox configuration page in the Depot CI settings.