Currently have a bug that is somewhat frustrating but able to bypass it. This is in Unreal 5.02
Steps to repro:
Create a default project.
Enable your mouse cursor.
Create a simple event attached to any button that uses the function Get Hit Under Cursor by Channel.
Branch from that to make sure you hit something, and then break the hit result.
Pass the Phys Mat output through a is Valid and attach a Print String to see if it is valid.
Add a cube with basic collision.
Go into project settings and create a physical surface type.
Create a Physics material and assign it this physical surface type.
Add the phys material to your Cube, press play and target it with your cursor event.
Results will always return invalid, and surface type returns default no matter the surface type. A simple but sometimes annoying fix is to then perform a line trace from the hit location of the cursor trace, and that will return the correct physical material.