Your real issue is that this demo.launch.py is configured (by default) to not publish TF on the standard /tf and /tf_static topics.

In your demo.launch.py you have this argument:

one_tf_tree = LaunchConfiguration('one_tf_tree')
one_tf_tree_cmd = DeclareLaunchArgument(
    'one_tf_tree',
    default_value='false',
    description='on true all tfs are published with a namespace on /tf and /tf_static')

So by default (false), Stage commonly publishes TF on namespaced topics like:

• /robot_0/tf

• /robot_0/tf_static

…and therefore you see no messages on /tf and /tf_static, which then breaks SLAM Toolbox (TF2 listens to /tf and /tf_static).

Fix option A (recommended): launch with one_tf_tree:=true

Run:

source /opt/ros/jazzy/setup.bash
source ~/nav_class_ws/install/setup.bash

ros2 launch stage_ros2 demo.launch.py one_tf_tree:=true

Then immediately verify:

ros2 topic echo /tf --once
ros2 topic echo /tf_static --once

If those print → TF is fixed and SLAM Toolbox will work.

Fix option B: change the default in demo.launch.py

Edit your file and change the default from false to true:

Before

one_tf_tree_cmd = DeclareLaunchArgument(
    'one_tf_tree',
    default_value='false',
    description='on true all tfs are published with a namespace on /tf and /tf_static')

After

one_tf_tree_cmd = DeclareLaunchArgument(
    'one_tf_tree',
    default_value='true',
    description='on true all tfs are published with a namespace on /tf and /tf_static')

Then re-run:

ros2 launch stage_ros2 demo.launch.py

One more note (important for SLAM)

Your demo loads cave_three_robots.world (3 robots). That’s heavy and causes “queue full” quickly. For SLAM teaching, it’s best to use one robot if you have a single-robot world/launch available.

Do this now (minimal)

1. Stop current demo (Ctrl+C)

2. Relaunch:

ros2 launch stage_ros2 demo.launch.py one_tf_tree:=true

3. Verify:

ros2 topic echo /tf --once
ros2 topic echo /tf_static --once

If you paste the output of ros2 topic list | grep tf after relaunch, I’ll tell you exactly which TF topic layout you’re getting (and what to use for SLAM params).