I’m facing the same turtlebot3_node problem:
In a new termin I typed the first command:
source ros2_ws/install/setup.bash
but it prompts:
user:~$ source ros2_ws/install/setup.bash
ROS_DISTRO was set to 'foxy' before. Please make sure that the environment does not mix paths from different distributions.
ROS_DISTRO was set to 'noetic' before. Please make sure that the environment does not mix paths from different distributions.
not found: "/home/user/ros2_ws/install/turtlebot3_node/share/turtlebot3_node/local_setup.bash"