Various small seasteading efforts have been started. But they have all been failures because there is insufficient economic incentive and value to these places.
Libertarianism in the formal sense, was developed by Rothbard as an ideological resistance movement. As were most of the liberty movements of the postwar and great society periods. I am not sure it’s arguable that it was not in practice an institutional model but an argument against institutional models.
Libertarianism, has been an ideological failure because his ethics were intolerable to too much of the population, just as Marxism, libertarianism’s opposite, is intolerable to most of the population.
The anarcho capitalist research program is attempting to find solutions to the problem of monopoly bureaucracy’s deterministic recreation of the totalitarian state. As a research program it’s been fruitful. And it is arguable that it’s possible to create a Hoppeian Private government. Even if not possible to create an anarchic society.
It may be possible to replace the bureaucratic monopoly state at some future date if we complete this intellectual exercise.
But at present, prospects are dim, because the intellectual work has not been sufficiently completed that it presents a viable social and economic alternative to the nation-state.