pf2e.fyi
From Pathfinder #153: Life's Long Shadows, which isn't enabled.

Improvisational Warrior

FEAT 9

When you use an improvised weapon, you apply the critical specialization of a brawling weapon to it. Depending on the shape and nature of the improvised weapon, your GM might determine another weapon group's critical specialization is more appropriate.

Pathfinder #153: Life's Long ShadowsOGL