We are loading test_data.json from https://github.com/readthedocs/readthedocs.org/blob/40bc5b1c01a8edfcaf4b898e5b79565598e36d51/readthedocs/projects/fixtures/test_data.json when running inv docker.up --init at https://github.com/readthedocs/common/blob/0620e5dad7831c8c6d093efb7e5c91d8118d9c61/dockerfiles/entrypoints/web.sh#L11

That fixture contains some projects that are old or are abandoned and are not good test cases to have under the development environment. It would be good to update them with better projects for testing. Those project includes test-builds, docs, sphinx-notfound-page, sphinx-hoverxref, blog and some other projects maintained by the community, like poliastro, geopandas, godot, numpy, xarray, sphinx, etc.