FreeFEM is a popular open-source finite element software. It is excellent for multiphysics because it allows you to write your own partial differential equations (PDEs). Highly flexible, great for advanced math. Cons: Script-based (no fancy "drag and drop" GUI). 2. Elmer FEM
Any claim of a "free license" outside these channels usually refers to cracked/pirated versions (with major risks). comsol multiphysics free license