EDGAR is the primary source for anything a US issuer is required to file: registration statements such as form-s-1, annual and quarterly reports, current reports on material events, proxy materials, form-4 insider transactions, schedule-13d and schedule-13g stakes, and form-13f institutional holdings.
It is free, timestamped, and full text searchable, which means you are reading the same document a professional reads at the same moment. Headlines summarising a filing are always downstream of the filing itself.
Two habits pay off. Use the full text search to find every filing that mentions a phrase, not just a company. And read the exhibits: the material contracts and risk factors attached to a filing usually carry more information than the body.