We use Orocos KDL for robot kinematics. Official download page: link.
Make sure you have previously installed Eigen3.
Installing KDL on Ubuntu is quite straightforward. Note that you will be prompted for your password upon using sudo a couple of times:
cd # go home
mkdir -p repos; cd repos # create $HOME/repos if it doesn't exist; then, enter it
git clone https://github.com/orocos/orocos_kinematics_dynamics.git
cd orocos_kinematics_dynamics/orocos_kdl; mkdir build; cd build
cmake ..
make -j$(nproc) # compile
sudo make install; sudo ldconfig; cd # install and go home