In my mind the ideas of socialism and libertarianism are polar opposites.
Wikipedia on left-libertarianism isn't too bad (https://en.wikipedia.org/wiki/Left-libertarianism), though notably missing a "Criticism" section.
Note that I don't endorse the views described in that article. I am expressing neither support nor opposition for left-libertarianism as a political philosophy. I have zero interest in debating the merits or demerits here at this time; I'm only trying to answer a question.
However, now I think that like Georgism/LVT, it is outdated due to the focus on Material means of production, and doesnt account for the increasing importance of white collar knowledge work.
https://en.wikipedia.org/wiki/Pierre-Joseph_Proudhon#Philoso...
They aren't necessarily libertarian socialism per se, but there area also lots of variations of socialism that combine social liberalism with economic socialism or which are fine with greater collectivism but reject central planning.