Peloton Bike & Bike+ owners can pause a Peloton on-demand class. They are unable to pause live classes. This feature was announced in November 2021. Your ranking is removed from the leaderboard is you pause a class.
Peloton Tread classes can not currently be paused, though the feature is said to be coming "soon".
Peloton Digital users have had the ability to pause classes in on-demand classes for a while, however, they don't show up on the leaderboard.