init 3 should not disable network access - thats a fault in debians systemd units - enable network and done
Right. On two siduction systems with wired ethernet
systemctl isolate multi-user.target
will stop networking. However
systemctl stop lightdm
will stop all user (init 5) processes, but it will leave networking up, so one can run d-u. On two siduction systems that are wireless only,
systemctl isolate multi-user.target
does not stop networking. So there is some bug in the conversion of sysvinit to systemd, that affects ethernet networking.