You can currently find the original 1994 film on several legal, free-to-watch platforms. Availability can shift monthly, but these sources are the most reliable:
: Includes insights from Director Roland Emmerich and Producer Dean Devlin, who discuss casting James Spader and Kurt Russell. stargate 1994 dvd free
: Features a dedicated 24/7 "Stargate" channel that loops the original movie alongside SG-1 episodes. You can currently find the original 1994 film