One Page Browser is the web browser that allows adding any web page as the Game Bar widget.
To use it as “Discord for Game Bar” set the address in the Settings to https://discord.com/app
How to use: https://redd.it/zdef7t

The keyboard support is not stable because of Game Bar limitations.
In case of using it with Discord, use the Discord mobile app QR code scanner to login. If you do not see the Discord QR code, enlarge the widget size.

Also, do not forget to install a popular game launcher for the game bar that supports the gamepad.
One Game Launcher: https://apps.microsoft.com/store/detail/one-game-launcher-beta/9PB82SFMMGRB