https://2e.aonprd.com/Rules.aspx?ID=2762

Proficiency without Level

This variant removes a character's level from their proficiency bonus, scaling it differently for a style of game that's outside the norm. This is a significant change to the system. The proficiency rank progression in Player Core is designed for heroic fantasy games where heroes rise from humble origins to world-shattering strength. For some games, this narrative arc doesn't fit. Such games are about hedging bets in an uncertain and gritty world, in which even the world's best fighter can't guarantee a win against a large group of moderately skilled brigands.