Best one I know of as a direct replacement is AWS PALACE: https://awslabs.github.io/palace/stable/ https://awslabs.github.io/palace/stable/ Of course, you have

Best one I know of as a direct replacement is AWS PALACE: https://awslabs.github.io/palace/stable/ https://awslabs.github.io/palace/stable/ Of course, you have to interact with the solver through JSON files and provide your own initial mesh. They recently added adaptive refinement but I don't know how well it works. Given what Ansys charges for an HFSS seat though can't complain!