"Far-left" is a derogatory term, a synonym for "left-wing extremist". Nobody considers themselves an extremist. I've noticed that my own views seem to be to the left of any mainstream political party here. For me, that just means that all the mainstream parties are right-wing.
I reserve the term "far-left" for hyper-dogmatic communist revolutionaries who don't object to using violence for political ends.
I don't agree that all Marxist-Leninists are authoritarian; and for what it's worth, I'm not aware of any Marxist-Leninist grassroots group operating here (UK).
I repeat: "far-left" is a term of abuse. It's routinely deployed by US persons of the Trumpian and Tea-Party persuasions against anyone they disagree with, including the leadership of the Democratic Party, a party that has never espoused any kind of socialism.