Mass units conversion

Dear all,
Previous to 2019, the definition of 1 g/mol (the standard LAMMPS mass unit) was equal to that of 1 amu, but the 2019 redefinition of SI units made that no longer true. Were changes made in LAMMPS to reflect this (i.e. uses the new SI definition), or does it still use the old definition of 1 g/mol (= 1 amu)?

No. Please see the discussion here: