OnePlus
Change the Default Browser App auf OnePlus
OnePlus uses a single default app assignment to decide which browser opens whenever you tap a link from another app, a text message or an email. This setting lives inside the Default apps menu and applies system-wide, not just inside one app.
If you installed Firefox, Opera or another browser but links still open in Chrome, the assignment was never updated after installation. New browsers get added to the list of available apps but never take over automatically, since OnePlus keeps the previous default active to avoid unexpected changes.
To switch it, go to Open the Settings ➔ Tap on Apps & notifications ➔ Tap on Default apps ➔ Tap on Browser app ➔ Choose the default Browser app. Selecting a browser here immediately routes all future links through that app.
This fix only works if the browser you want is already installed. If a browser is missing from the list, install it first, then repeat the steps above.
Changing the default does not delete data or bookmarks from the browser you stop using; it only changes which app handles new links going forward.