The definition of an "online" system in the context of networking can vary depending on the services being used.
Ubuntu has created a specification to define what an "online" system should be for their distro, aiming to avoid delayed boot times.
Netplan, a unification layer for networking daemons in Ubuntu, has introduced functionality to tweak the behavior of systemd-networkd-wait-online.service.
Future work includes enhancements to NetworkManager-wait-online utility for better control over specific networking states.