Three of the provinces were looking to make home advantage count in the first round of the BKT United Rugby Championship, while Leinster began their title defence in South Africa.
Fit-again Ireland international Mack Hansen made his first appearance for Connacht since last October, as Stuart Lancaster's men hosted the DHL Stormers at Dexcom Stadium.
28-26 winners over Edinburgh in pre-season, Ulster welcomed the Scottish capital side to Affidea Stadium with eight debutants in the province's matchday squad.
