There may be some dissident leftists that are sincere. In terms of media figures Glen Greenwald and Jimmy Dore come to mind. They are left wing outcasts that are largely shunned by the MSM though, although certainly not demonized or deplatformed the way the dissident right is. In terms of mainstream leftists no, they are almost all frauds, and in terms of "woke" leftists, IE leftists that focus on shit like BLM or immigration, they are all frauds, at least the white ones.