Being a Lennart is the male equivalent to being a Karen. A slightly annoying behavior and considered to be a know-it-all Lennarts tend to be a mix of conservative and liberal snow flakes with a hefty pinch of racism. If you have fears of some kind of muslim takeover you are a Lennart. If you really like to portray minorities as security issues you probably are a Lennart. If you want to speak the manager when being treated by a black guy you are most definitely a Lennart.
A somewhat well-known author of surreal horror fiction from Germany, Lennart Poettering is mostly known for writing overly long and confusing works such as Pulsations of Autophilia (a tragedy about a sluggish autistic teenager who is murdered while fucking his uncle's Porsche and comes back as a ghost to seek vengeance) and Systems Down (about a server administrator who finds himself locked in the server room after closing time with a horrible, memory-corrupting abomination).