Please make sure you are using the latest version of dcm2niix (v1.0.20201102), which improves support for GE meta data
  https://github.com/rordenlab/dcm2niix/releases/tag/v1.0.20201102
I am well aware of the NAMIC DTI web page (I am a contributor). You can find additional details on how dcm2niix supports GE data here:
  https://github.com/rordenlab/dcm2niix/tree/master/GE

Also, please make sure that your DICOMs are direct from GE. For example, the ABCD study creates their own DICOM images from data that is acquired on GE scanners, and their format does not include much of the rich meta data useful for analyses. This is a limitation of the DICOM files provided by the ABCD team, not of dcm2niix.