> if that's the case then surely Russia has agents masquerading as the far left too?
Yes; that's well established (while it's less talked about, the 2016 operation included promotion of Stein and Sanders as well as the more intense promotion of Trump, and also included false-flag promotion of in-person left-wing and right-wing demonstrations at the same time and place with the intent of fomenting political violence.)
Russia’s government also had connections to groups pushing “Calexit” after the election, including those pushing it as a defense against Trump.
Russia’s government also has connections, and has overtly funded, groups seeking restoration of the Hawaiian monarchy.