SourceGraph is GIT Code search platform and in many corporate environment works as a one stop for all GIT searches/lookups regardless of git implementation (gitlab, github, ...).

NBVIEWER works with open (non-authenticated) SourceGraph e.g. https://sourcegraph.com/github.com/ContextLab/storytelling-with-data/-/raw/data-stories/spotify/.ipynb (is a raw file, full file in UI here https://sourcegraph.com/github.com/ContextLab/storytelling-with-data/-/blob/data-stories/spotify/.ipynb ) however it does not support SourceGraph authenticated endpoint typically used in corporate environments typically done using auth token.