“Other libertarians recognize the essential role sovereignty plays in protection of liberty.”
You’ll hear things along the line of “if there’s no welfare state, there’s no problem with an open border”. Partially true. The Libertarian platform would be hunky dory if there was little economic and cultural disparity in the world.
With regards to ending the welfare state and having an open border, the order in which those two things happen is crucial to the outcome.
End the welfare state first, and an open border (with some nominal checks for security purposes) might be feasible. Opening the borders first - as has happened - invites a globe full of benefit-seekers to come and suck the life out of the country.