XBOX Keyboard and mouse

Ok, so firstly you should be able to just plug in the mouse/keyboard USB and use it (if they are supported) you shouln't need an adapter to use mouse and keyboard on Xbox One since mouse and keyboard support has been added.

Secondly I'm not aware of black ops 4 supporting mouse and keyboard use on console, so if the developers have not enabled mouse and keyboard support on Xbox One, then using an adapter to be able to use your mouse and keyboard will be considered cheating.

For the following to work you must make the menu selections using your keyboard. If you use the controller to make your menu selections to start the game you will be placed in a room for those with a controller and your keyboard/mouse will be non functional
to make it fair to other players. To enter the room for keyboard and mouse users the game must be started by selecting the options using the keyboard/mouse. Hope this helps.

Mouse and keyboard support

Fortnite on Xbox One supports the ability to play with a mouse and keyboard. Note that when using a mouse and keyboard on Xbox One, you’ll be placed in a game with other users who also chose mouse and keyboard as their control option. To enable your setup
to use mouse and keyboard, see Mouse and Keyboard Support

Note If you’re on a child account, you’ll also need to enable settings for cross-network play to use a keyboard and mouse while playing
on Xbox One.

you can use mouse and keyboard on xbox now, even microsoft sell an xbox keyboard. ps4 is now starting to support mouse and keyboard.

Hi Ben Lewandrowski,

Currently there is keyboard and mouse support, but its up to developers of those games to add the option to allow it. Warface is not one of them that allows keyboard and mouse support yet. I can see that it is an upcoming title for keyboard and mouse support
soon. More information about keyboard and mouse developer support HERE.

Current and upcoming titles that do or may support keyboard and mouse
HERE.

the original Xbox only came with a controller. the Xbox 360 only came with a controller. the Xbox One comes with a controller. you can't buy an Xbox One with a Keyboard and Mouse.
in my opinion if they don't sell them with a Keyboard and Mouse they shouldn't have support for Keyboard and Mouse. if you want to use
Keyboard and Mouse you should play on a PC and not on a console.