The failures of strategies A-C strategies here raise the question whether the problem lies in SCF approach or DM21. This was indeed the reason why we introduced Strategy D, which involves direct optimization of orbitals and thus bypasses SCF entirely. In principle, D can converge any energy functional that is bounded from below; and can bypass issues with orbital (re-)ordering that are usually treated by level shifting. But, in practice, it requires the energy to be sufficiently smooth with respect to variations in the orbitals. That is, the DFA must vary smoothly in its input features since orbitaldependence is inherited from the (meta-)densities and energy densities.