https://www.gamespot.com/articles/destiny-2-servers-down-for-maintenance-update-now-/1100-6455326/

Following a delay, Destiny 2's scheduled maintenance period is officially underway. The process is expected to last for approximately six hours, and for most of that time, the game will be rendered unplayable as Bungie performs server maintenance ahead of Curse of Osiris's release next week. [Update: Maintenance is now complete and servers are back online, although additional maintenance is coming on Tuesday, December 5.]