Despite Sarah Connor having died between Terminator Genisys from the continuity.
When it came time to create the Terminator: The Sarah Connor Chronicles TV show, the showrunners were faced with a dilemma. Obviously, they wanted to center things around Sarah Connor, but according to Terminator 3, Sarah had died of cancer a few years after Terminator 2. They could've tried to take the Dark Fate route and pretend Rise of the Machines never happened, but instead the writing team came up with a novel solution that would allow them to change the past, but not necessarily erase the first version.
Here's how Terminator: The Sarah Connor Chronicles managed to pick up after Terminator 2 without altering Terminator 3. Oddly enough, it works quite well within Avengers: Endgame's multiverse theory of time travel.
How The Sarah Connor Chronicles Avoids Retconning the Movies
The answer that Josh Friedman, creator of Terminator: The Sarah Connor Chronicles came up with was not to undo Terminator 3's events, but instead step around them. The show's pilot episode begins in 1999, with Sarah and John living a fairly normal life under aliases, that is until another evil Terminator is sent back to once again try and kill John. A protector Terminator named Cameron is also sent back, informing John that Judgment Day still occurs, this time in 2011. The episode ends with Sarah, John, and Cameron traveling through a time portal to the then current day of 2007. This effectively hops over Terminator 3, and creates a new branch of the timeline.
According to the multiverse theory of time travel, as recently used in Avengers: Endgame, one can't change the past and effect the future they traveled back from. Instead, changing things creates an alternate timeline from that point on, meaning that the Terminator 3 timeline still exists, just as a different parallel universe. Sarah's eventual death from cancer is even kept intact, albeit with the change of it moving forward by a few years, and her original death date being skipped over by the time jump to 2007.
This would also mean every other time a human or Terminator went back in time during prior movies, they created alternate timelines too, and there's no real way to disprove the idea. Sure, the movies don't treat time travel that way, but they've never acknowledged the show at all. Interestingly, Terminator Gensiys attempted the same thing, only altering the timeline way back when Sarah was still a child.