Yes, restoring pkl files on some other machine is usually tricky. If the authors provide a model.pkl file, it could technically be at least any of the three
a) a model pickled via regular pickle use
b) a model saved via pickle using torch.save
c) a model state_dict saved via pickle using torch.save
So, it’s maybe best to ask the authors for recommendation for loading it. Also, you may look through their other source code and see if you can find a file that created this pickle file, which could give you additional clues.