I played through Hogwarts Legacy this summer. Have to say I enjoyed it more than I thought I would. I later realized that it is possible to visit Azkaban — but only if you picked Hufflepuff as your house. I played through the game as a Gryffindor student, so I started a new game to be able to play the Azkaban mission. I couldn't find super clear instructions on how to activate the mission. They were all like: "Rescue the old lady at the Black Lake and you will receive a letter to activate the mission". So here it is.
How to visit Azkaban in Hogwarts Legacy
You will not miss it. Just play through the first main story missions, and you will unlock the mission Prisoner of Love.
- Complete the first four classes (Charms class, Defence Against the Dark Arts class, Herbology class, and Potions class).
- Rescue Nora Treadwell at the Black Lake.
You will then get a letter from Lenora Everleigh saying you should speak to Eldritch Diggory in the Hufflepuff common room.
That's pretty much it.