hunspell-de-at software package provides Austrian (German) dictionary for hunspell, 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 hunspell-de-at
hunspell-de-at is installed in your system.
Make ensure the hunspell-de-at package were installed using the commands given below,
$ sudo dpkg-query -l | grep hunspell-de-at *
You will get with hunspell-de-at package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Text Processing |
| Package | hunspell-de-at |
| Version | 20160407-1 |
| Description | Austrian (German) dictionary for hunspell |
| Sub Section | Text |