TF information not available in TF Tree

[AllenIsaacJose]

• OS: Ubuntu 22.04
• ROS 2 Distro: Humble
• Built from source or installed: installed
• Package version: 2edd54c

Expected behaviour
The frames are visible in ros2 run rqt_tf_tree rqt_tf_tree and also in the drop down list in Fixed Frame in Global Options in RViz2.

Actual behaviour
No tf data received in RViz and also in tf_tree.

To Reproduce
Provide the steps to reproduce:

1. Create a robot.yaml file with a random namespace name and run the simulation.
2. ros2 run rqt_tf_tree rqt_tf_tree - to see that no tf data is received.
3. rviz2 - to see that the drop down list is empty in Fixed Frame in Global Options.

Other notes
If we set no namespace, that is namespace: /, then the tf data is received in RViz and also in tf_tree. That is, when a namespace is provided, tf_static topic are published under /tf_static and /tf_static topic is empty.

[AllenIsaacJose]

Partly fixed using remapping the topics as seen below:

ros2 run rviz2 rviz2 --ros-args -r /tf:=/NAMESPACE/tf -r /tf_static:=/NAMESPACE/tf_static -p use_sim_time:=true
ros2 run rqt_tf_tree rqt_tf_tree --ros-args -r /tf:=/NAMESPACE/tf -r /tf_static:=/NAMESPACE/tf_static

But in case if we spawn 2 robots, how can be done in a similar way?(In the above method, I could only remap the topics for 1 robot). Some of the example which i saw in github utilizes prefix to seperate different TF trees, but all the information are published on the same /tf topic instead of /NAMESPACE/tf.