Ceres uses dual numbers
https://github.com/ceres-solver/ceres-solver/blob/master/inc...
This library from google is used everywhere in robotics, so it's hardly some backwater little side project.
So does c++ autodiff https://github.com/autodiff/autodiff/blob/main/autodiff/forw...
So does Eigen: https://eigen.tuxfamily.org/dox/unsupported/AutoDiffScalar_8...