LeoRover not moving upon TeleOp

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Hello,

I've cloned the leo_common repo & spawned this LoeRover in gazebo using the below launch file:

<?xml version="1.0"?>
<launch>
  <arg name="model" default="$(find leo_description)/urdf/leo.urdf.xacro"/>
  <param name="robot_description" 
         command="xacro --inorder $(arg model)"/>

  <!-- Spawn the robot model in empty world-->
  <node name="spawn_xacro" pkg="gazebo_ros" type="spawn_model" output="screen" args=" -param robot_description -urdf -x 0 -y 0 -z 1 -model model" />
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
  </include>
</launch>

Then I followed the instructions here & tried to teleop with keyboard using rosrun leo_teleop key_teleop. I'm getting the following message printed to terminal

Waiting for subscriber to connect to /cmd_vel
Waiting for subscriber to connect to /cmd_vel

I think it's printed by this line from teleop_twist_keyboard package. As it suggests, there are no subscribers to the /cmd_vel topic.

My questions:

1) What subscriber should subscribe to the /cmd_vel topic?

2) Are there any controllers already written for the LeoRover?

Note: I'm running ROS Noetic on Ubuntu 20.04.