Hello Daniel,
Does the error occur if you try to load the rosbag data outside of the Lidar Labeler?
bag = rosbag(filePath);
msgs = readMessages(bag, 1); % Testing with just the first message to start, try more if it works
If the error occurs, my suspicion is that you are seeing a library conflict between the ROS MATLAB libraries and the installed ROS libraries and their dependencies. MATLAB uses ROS Melodic, while you have ROS Noetic installed, so there will be a fair number of different library versions.
Try starting MATLAB without having sourced ROS Noetic and without pointing towards the installed Noetic folders. You may have to double-check your PATH and LD_LIBRARY_PATH environment variables to make sure that no "noetic" folders are still present before starting MATLAB.
It would be helpful to see exact error messages too, at least to make it easier for other users to find this post.
-Cam
