It is a mod for the game. Currently, when you hover over an interactable object, you will see the gamepad's buttons displayed in the top right corner of the screen. But this will not display the correct gamepad button binding when you are holding your device in your hand.

With this modification, you will be able to fix this problem. You will need to create a new config file with a new section. In this section, you will need to specify the button name yourself as it will not be automatically detected in-game (or download one of the preconfigured packs).

If you downloaded one of the preconfigured packs, then you will need to copy the plugins and config folders into Valheim BepInEx.