Pathfinder 2E - PF2 Remastered - Does attack of opportunity still exist, or was it replaced by react

In Pathfinder 2, Attack of Opportunity was a feature not every class got. Fighters got it at first level for free, but Barbarian, Champion, Magus and Swashbuckler could take it as a 6th level feat. None of those classes are in Player Core 1, but they will get Reactive Strike in AoU's place.
It should also be noted that most creatures don't have it, either.

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