Can I play Rainbow six siege with keyboard and mouse in 2023? And if so how?

No you can not use keyboard and mouse on Xbox One Rainbow Six siege. I strongly advise you not to buy any adapter and play Keyboard and Mouse as it is considered as cheating.

Some games do not support mouse and keyboard such as rainbow six siege

If you want to use a keyboard and mouse on Rainbow Six Siege, then you can either purchase the PC version of the game or contact Ubisoft and ask them to include mouse and keyboard support in the console versions.

I do not think currently Rainbow Six Siege are compatible with keyboard and mouse on the Xbox One.

Also An Adapter is considered cheating so I wouldn't use one.

Here's how you can do it on Xbox One:

Connect your keyboard and mouse to your Xbox One console. You can connect them directly to the console's USB ports or use a USB hub if you need more ports.

Once your keyboard and mouse are connected, start up Rainbow Six Siege on your Xbox One.

In the game's main menu, navigate to the Options menu.

From the Options menu, select the Controls tab.

From the Controls tab, select the Controller Type option.

Change the Controller Type to Mouse and Keyboard.

Customize your keyboard and mouse settings to your liking.