where |∆𝐸| FFFFFF . is the mean absolute value of all the reference energies from 𝑖 = 1 to 55, 𝑁 . is the number of systems in each subset, 𝑀𝐴𝐷 . is the mean absolute difference between calculated and reference energies for each of the 55 subsets. For the details of all 55 subsets with proper references, see Table in ref. All electronic structure calculations were performed using the QCHEM 5.4 package on the ChemFarm HPC cluster in the Faculty of Chemistry at the Weizmann Institute of Science. The Weigend-Ahlrichs def2-QZVPP basis set was used for all subsets except seven, where we used the diffuse-function augmented variant def2-QZVPPD 49 instead: the rare gas clusters RG18 and the six anion-containing subsets WATER27, IL16, G21EA, BH76, BH76RC, and AHB21. For the C60ISO and UPU23 subsets (which have comparatively small weights in WTMAD2), we settled for the def2-TZVPP basis set to reduce computational cost. For the remaining 46 subsets, the def2-QZVPP basis set was used. The corresponding standard RI-MP2 and Coulomb-exchange fitting (RI-JK) basis sets were employed throughout to reduce the computational cost further. The large pruned integration grid SG-3 was used across the board. Generally, inner-shell orbitals were frozen, but in subsets where such orbitals come close enough to the valence shell to qualify as 'honorary valence orbitals', the same frozen-core settings were used as in Refs. Similar to the unregularized (x)DSD functionals, one fully optimized κ-DSD also has six adjustable linear parameters: cX,HF, cC,DFT, c2ab, c2ss(=c2aa+c2bb), and for the D3(BJ) dispersion correction, one prefactor s6 and one parameter a2 for the damping function (like in refs we constrain a1=s8=0). On top of that, our new κ(x)DSD functionals also contain the PT2 regularization parameter κ.