As of this moment the 2020 Dallas Cowboys season is scheduled to begin, in terms of games that matter, on September 13th on the road against the Los Angeles Rams.
The Cowboys are scheduled to play five exhibition games before that, including the Hall of Fame game. Preseason games are huge for on-the-bubble players and are where some guys have earned their spot on the regular roster. They obviously do not have the sex appeal of regular season games, but they are undoubtedly important.
Things are still very much up in the air thanks to the COVID-19 pandemic.