$ wget https://ftp.gnu.org/gnu/help2man/help2man-1.47.16.tar.xz
$ tar xvf help2man-1.47.16.tar.xz
$ cd help2man-1.47.16/
$ mkdir build
$ cd build
$ ../configure --prefix=/opt/help2man/1.47.16
$ make
$ make install

$ export PATH=/opt/help2man/1.47.16/bin:${PATH}
$ export LD_LIBRARY_PATH=/opt/help2man/1.47.16/lib:${LD_LIBRARY_PATH}