IBAMR is software for simulating fluid dynamics, solid mechanics, and fluid-structure interaction (FSI). It offers leading community implementations of the immersed boundary (IB) method and its extensions, and it achieves high performance through its support for block-structured adaptive mesh refinement (AMR). This project enabled us to develop new computational infrastructure within IBAMR, including: 1) support for additional geometrical descriptions, including CAD-based geometries, for the immersed structures; 2) efficient adaptive multiphase flow solvers, including for low Mach number reacting flows and multiphase complex fluid flows; 3) new algorithms for rigid- and flexible-body FSI using interfacial fluid-structure coupling methods; and 4) scalable fluid-solid partitioning and coupling algorithms to provide high performance at extreme scales. Each of these capabilities is motivated by and anchored in specific applications led by one of the project PI/Co-PIs, including cardiovascular, esophageal, and pulmonary medicine and biology; wave energy converters; and additive manufacturing.