[Dagger2]

> It looks like doing this has the disadvantage that it erases the baked-in "This shouldn't be used for global-scope transmissions.

I tried with the kernel-generated LL and my kernel does attempt to use a link-local source when connecting to GUA addresses if it has no other address to connect from. And it works:

  # ssh 2001:db8::1 env | grep CLIENT
  SSH_CLIENT=fe80::f0b3:20ff:fe3d:d4cf%eth0 54456 22

(...so long as the destination is on the local network. In this case I assigned 2001:db8::1 to the router, but the router will issue an ICMPv6 redirect for other IPs on the network, which is awkward for me to test but should also work.)

I note that you didn't run `ip route add fe80::/64 dev enp0s3` after adding the LL with noprefixroute, which... seems to break surprisingly little? Because the packet gets sent to the router, which does still have a route for fe80::/64 to the same network, so it issues an ICMPv6 redirect and the client ends up doing NDP anyway.