The framerate cap to 30 in the Assassin's Creed Shadows den is a bug that will be fixed

Whether in “Quality”, “Performance” or even “Balanced” mode on compatible screens, the Den’s framerate in Assassin’s Creed Shadows remains locked at 30 FPS.

Ubisoft had never really spoke on the matter, and many thought it might be a deliberate technical limitation on the part of the studio. In reality, it’s a bug that prevents the game from running properly in this location, which players can customize as they go along.

The developers confirmed the information on Reddit. They will be patching it on the PS5 and Xbox Series versions soon enough.