GTA 6 unlocks at midnight local time, and boxed copies have no disc
Midnight on 19 November wherever you are, on PS5 and Xbox. Boxes in shops contain a download code.
Rockstar Support says GTA 6 unlocks at midnight local time on 19 November in every region, on both PS5 and Xbox Series X|S.
Boxed copies go on sale on 12 November, but they contain a download code, not a disc, and only for the Standard Edition. PS5 codes only work on a PlayStation account from the same region as the box. Xbox codes work anywhere.