All DFT calculations in this work have been obtained in PySCF . We use the TMC151 20 transition-metal datasets compilation, developed by Chan et al., to assess the accuracy of DM21 in TMC. TMC151 includes the TMD60 dataset , featuring TM dimer dissociation energies; MOR41, with 41 metal-organic reaction energies ; and TMB50 containing barriers of complexes of secondand third-row transition metals . The current implementation of DM21 is very costly. For example, a single SCF iteration for n-decane on 8 CPU cores with a def2-QZVP basis set takes approximately 7 hours, whereas a complete B2PLYP double hybrid calculation with the same settings is completed in about 13 minutes. Therefore, due to the currently high cost of DM21, we excluded reactions with large systems from MOR41 and TMB50, leading to their TMB40 and MOR17 subsets, respectively. TMD60 was kept as is, leading to the streamlined TMC117 subset of TMC151 (TMB40 + MOR17 + TMD60). For TMD60 calculations, we use the def2-QZVP basis set, while for TMB40 and MOR17 we use the def2-TZVP basis set (with corresponding effective core potentials as in Ref. for heavier atoms when applicable) . Resolution of identity approximations are used with corresponding auxiliary basis sets to accelerate the calculation.