>What I find confusing about this comment is that to me, authoritarian and libertarian are opposites, but have only to do with individual freedoms, not the political system.

"Do whatever the F you want as long as you don't challenge the state" isn't that incompatible at first glance and might work ok if you have a low touch state. Where it gets obviously incompatible is when you have eastern european style oligarchs and western style administrative state and state favored businesses and industries that leverage state violence to stifle competition.

I don't think it's possible to have an authoritarian government in a modern society that doesn't trend in one of those directions.

There have been such dictators in the past. Singapore is one example. Arguably the British Empire was libertarian by the standards of its time (and empires).

Perhaps the least recognized example is America. The Constitution imposes libertarianism on the population against majority will. You can't change the constitution with a 50%+1 vote, so it forces freedom of speech and other rights on people who might otherwise easily vote to get rid of them. There's no one man enforcing the constitution, just a general agreement to obey SCOTUS.