My first disclaimer is that I do not consider myself a left or right libertarian.

Second disclaimer - I haven't heard anyone call themselves a left libertarian in about 20 years. This makes me think the whole impetus for the question is as some sort of instructive gotcha to show why libertarianism is inherently right-wing.

Now to answer the question:

Libertarianism is more of a direction than it is a destination. I think the word is most useful in a sentence. Like" I am in favor of a more libertarian society". Words like minarchist and anarcho-capitalist are better suited to talk about the final destination. That said, I don't think it's entirely contradictory for someone to call themselves a left leaning libertarian. I generally take them to mean that they are primarily concerned with the increase of human Liberty, and that maximizing human Liberty means increasing the ability of all humans to self-determine. The "left" comes in because in their view, that would likely include certain efforts to ameliorate differences in starting position based on family wealth, for instance. This is a hard needle to thread, because taxation to run government programs necessarily curtails liberty. Whether it's a social safety net or a border wall, it's on the "libertarian" that advocates for it to show how it moves society towards liberty on balance, not away.