Is Liberty City in GTA 6?
The direct answer
No — not as a playable location. GTA 6 takes place entirely in Leonida, though Liberty City is referenced in Lucia’s backstory.
The GTA 6 map is the state of Leonida (Rockstar’s Florida). Liberty City, the series’ New York, is not part of the playable world.
There is a lore connection: Lucia is described as having roots in Liberty City before coming to Leonida. That’s a story reference, not a visitable location in the game.