The standard authoritarian scales are indeed tuned to detect right-wing ideology. That being said, it's easy (though unpopular) to construct measures that capture Left-Wing Authoritarianism (the "Loch Ness Monster," as Altemeyer famously labeled it). Unsurprisingly, authoritarianism turns out to exist in equal measure on left and right. A couple samples of the literature; there are plenty more if you google around:
[1] https://onlinelibrary.wiley.com/doi/full/10.1111/pops.12470 [2] http://www.bartduriez.com/sites/default/files/documents/PDF/...