It can be a chore to figure out exactly how to watch The Defenders and the related MCU TV shows that originally aired on Netflix (but are now available exclusively on Disney+), but release order matches un-universe chronology and is the best approach. Daredevil, Jessica Jones, Luke Cage, and Iron Fist all received their own series to set up the characters before coming together in their entirety for the first time in The Defenders. The approach mirrored the MCU’s success on the big screen, though the Defenders Saga shows’ collective MCU canon status is still up in the air.
https://screenrant.com/daredevil-defenders-netflix-marvel-timeline-best-order/