A way forward in ML of XC approximations able to capture different correlation regimes (from weak to strong) is to use fully nonlocal features (i.e. containing information about the electronic density everywhere). Then the question arises: what is the form of the fully nonlocal features that can be used? While some very recent ML XC models attempted to make use of different nonlocal features , the strongly interacting limit (SIL) of DFT provides a natural and theoretically firm ground for the development and utilization of the fully nonlocal features. Specifically, the rigorous mathematical treatment of the SIL reveals that the building blocks of the exact XC functionals arising from the SIL are very different from the standard Jacob's ladder features. . Instead of semilocal quantities and KS orbitals that form the Jacob's ladder, in the SIL, we see specific integrals of the density encoding fully nonlocal information. For general (3D) geometries, computing the exact SIL is prohibitively costly, which in turn inspired the construction of functionals (with the N 3 scaling) that either approximate the SIL or are inspired by the SIL features. For example, the nonlocal radius and shell model , have been proposed to approximate the SIL and retain some of its nonlocality. On the other hand, the recently proposed fully nonlocal multiple radii functional (MRF) draws from the main structural motifs of the SIL, but approximates electronic energy at the physical regime instead of the strongly interacting one.