I guess you were underwhelmed by the boss in the hut at the end of chapter 2? It is indeed designed as a "story" encounter and not at all as a challenging one.
Don't worry, there are some more interesting bosses coming your way. 🧚
The puzzle solution is in the two notes you find in the house ("North - West - ..." and "... - East - South-East").
After entering the room hidden behind the sandfall, you need to go North, then West, then East and finally search the South-East walls. If you interact at the right place, a bubble with a question mark will appear. If you interact a second time, a secret stair will appear.
If you are stuck again, there is a Walkthrough.docx file to guides you through the main quest.
