OnePlus
Change Default Apps auf OnePlus
OnePlus phones assign one app per function, such as browser, messaging or digital assistant. Android keeps using that assignment even after you install a better alternative, because the system never re-asks which app should handle a task unless you tell it to.
This is controlled through Open the Settings ➔ Tap on Apps & notifications ➔ Tap on Default apps. From this screen you see every category with a default app assigned, including Assistant & Voice input. Tapping a category shows all installed apps that can fill that role, and selecting a different one switches the assignment immediately.
This fixes cases where links open in an unwanted browser, or where a voice command launches an assistant you stopped using. It will not help if the app you want is missing from the list entirely. In that case the app usually needs to declare support for that role, so reinstalling it or checking for an update is the better first step.
Switching a default app has no effect on your data or saved settings inside the apps involved. Only the system-level link between the action and the app changes, and you can switch back at any time from the same screen.