VGTimes says GTA VI will ship with 55 trophies or achievements that can all be earned in single player, with 54 standard PS5 trophies plus a Platinum, and an equivalent Xbox list that swaps the Platinum for a Mythic Achievement. The report says online content would not be required to complete the set.
The article does not name where the list comes from, and Rockstar has not published a trophy list, so we are classing this as an unverified rumor. For comparison, the report cites 51 trophies for GTA V and 52 for Red Dead Redemption 2. Any GTA Online trophies would presumably come as a separate set later, which is the writer's expectation rather than a reported fact.
Why it matters: if accurate, completionists could chase the Platinum from the campaign alone without waiting on online modes. Treat the number as provisional until the PlayStation Store and Xbox listings go live around preload.