You cannot. To have KOKKOS with GPU supported, the KOKKOS package needs to provide some introspection function that allows to detect safely through the library interface whether GPU support has been enabled and a viable GPU is present. This is currently only available in the GPU package. Also, the KOKKOS package has the requirement that if you compile it for a GPU, you must use the GPU. You cannot use only threading, which is makes supporting it very complex.
So your options are, either use the GPU package or compile KOKKOS only with threads and not with GPU support or don’t use LAMMPS-GUI or implement the necessary introspection function(s) into the LAMMPS C++ code.