The documentation states that we need to call
ros2 launch turtlebot4_ignition_bringup ignition.launch.py
To launch the simulation with the turtlebot. However, this resulted for me in launching the simulation but without any turtlebot spawned. Instead, calling ros2 launch turtlebot4_ignition_bringup turtlebot4_ignition.launch.py did launch the simulation with the spawned turtlebot.
I believe there is a mistake in the documentation on the page:
https://turtlebot.github.io/turtlebot4-user-manual/software/simulation.html
The documentation states that we need to call
ros2 launch turtlebot4_ignition_bringup ignition.launch.py
To launch the simulation with the turtlebot. However, this resulted for me in launching the simulation but without any turtlebot spawned. Instead, calling
ros2 launch turtlebot4_ignition_bringup turtlebot4_ignition.launch.py
did launch the simulation with the spawned turtlebot.