OnePlus
Add a New Keyboard auf OnePlus
Installing a keyboard app from the Google Play Store only copies it onto the device. Android and OxygenOS do not activate new input methods automatically, since a disabled keyboard cannot read or send any keystrokes until you grant it permission.
This safety step exists because a virtual keyboard has access to everything you type, including passwords. OxygenOS therefore requires you to confirm each new keyboard manually before it becomes available in the keyboard switcher.
Where to enable a new keyboard
Go to Open the Settings ➔ Tap on System ➔ Tap on Languages & input ➔ Tap on Virtual keyboard ➔ Tap on Manage keyboards. Find the keyboard you installed and use the toggle to enable it, then confirm with Turn on.
Once enabled, the keyboard appears in the keyboard picker, but it does not automatically become your default input method. You still need to switch to it manually while typing, for example from the keyboard switcher icon in the navigation bar or notification shade.
If the keyboard is missing from the Manage keyboards list entirely, check that the app finished installing and that it was not disabled by battery optimization or app permissions.