flwm-dbg software package provides Fast Light Window Manager (debugging symbols), you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install flwm-dbg
flwm-dbg is installed in your system.
Make ensure the flwm-dbg package were installed using the commands given below,
$ sudo dpkg-query -l | grep flwm-dbg *
You will get with flwm-dbg package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | X Window System software |
| Package | flwm-dbg |
| Version | 1.02+git2015.04.29-1 |
| Description | Fast Light Window Manager (debugging symbols) |
| Sub Section | X191 |