Is talking about something everybody already knows still Lashan Hara? Could you provide sources for further learning?
Lashon Hara — gossiping — is a negative character trait.
Although the technical problem of libel will not apply to something that is already known to everybody, doing so without cause remains a transgression of the prohibition, because it expresses the negative trait of aimless gossiping, which is bad in itself.
The Chafetz Chaim thus mentions that even concerning something that people know, if one’s intention is for the bad, to further spread the information and to relish doing so, it remains forbidden.