Hi,
FreeCad also permits the conversion of .stl to .step using a simple procedure.
However, it is prone to fail and F360 to freeze for complex geometries. In that case, I only succeeded by manually simplifying the mesh, if necessary, further simplifying using, e.g. F360, and afterwards trying to convert. The success rate is low, and it demands a significant effort.
Another option is meshmixer, but with additional complexity (at least for me).