Libertarian socialism is an anti-authoritarian and anti-capitalist political current that emphasises self-governance and workers' self-management. It is contrasted from other forms of socialism by its rejection of state ownership and from other forms of libertarianism by its rejection of private property. Broadly defined, it includes schools of both anarchism and Marxism, as well as other tendencies that oppose the state and capitalism.

Wikipedia - Libertarian socialism

It's usually a synonym for Anarchism.

The oxymoron "Libertarian Capitalism" is an propagandistic rebranding of landlord feudalism, engineered by a right-wing grifter who thought Adam Smith was a pinko commie.

It's taken seriously by the folks who despite all of the evidence, think trickle-down economics is a good idea. It's a joke to everyone else.