One more thought then:
dpkg -s ros-noetic-<pkg> will give you info only if installed. Either using that or another dpkg tool, you could find if the base ROS binary is installed as a way to know if ROS is around, e.g. dpkg -s ros-<distro>-ros.
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One more thought then:
dpkg -s ros-noetic-<pkg> will give you info only if installed. Either using that or another dpkg tool, you could find if the base ROS binary is installed as a way to know if ROS is around, e.g. dpkg -s ros-<distro>-ros.