Ur_gazebo pkg from universl_robot github is not working rospack doesent recognise as a package
If you are referring to ros-industrial/universal_robot this is currently under some change. For ROS melodic and noetic, please use the melodic-devel-staging branch.
Alternatively, you can use my fork’s calibration_devel branch which is the GoTo-version for our current ROS driver and therefore should always be kept at a workable state.
I hope that we will sort out this complicated situation soon.