figtree software package provides graphical phylogenetic tree viewer, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install figtree
figtree is installed in your system.
Make ensure the figtree package were installed using the commands given below,
$ sudo dpkg-query -l | grep figtree *
You will get with figtree package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Science |
| Package | figtree |
| Version | 1.4.2+dfsg-2 |
| Description | graphical phylogenetic tree viewer |
| Sub Section | Science |