I have seen that some articles calculate Hubbard $U$ value self-consistently using Quantum Espresso code. Then, they use it in VASP calculations. My question is: In which conditions can this value be transferred from a code to another?
I have looked into this a bit, I think in general it is ill-advised to mix codes like this unless it is needed, but VASP does not support self-consistent hubbard U (no perturbations at non-zero U). As long as you can prove the two codes produce the same results, it is probably okay. Specifically, if you can prove the property of interest is the same at U=0 and U=Uscf, then I would not be too skeptical though.
The main issue here is the U parameter is dependent on everything about the system. Energy cutoff, grids, psuedopotentials, etc. could all make a difference so it should probably not be directly used without checking that band gap is the same for example.