Linear Mono

Sounds to me like regular “16-bit WAV”, 8 kHz sample rate, mono.
Yes you can do that with Audacity 2.2.1, but upgrading to 2.2.2 at your earliest convenience is highly recommended as the new version has some important bug fixes.

First you need to ensure that your track is mono. If you have a stereo track, you can mix it to mono:
Select the track (click on it), then
“Tracks menu > Mix > Mix Stereo to Mono”

Second, set the “Project Rate” to 8000 (bottom left corner of the main window.

Then export as 16-bit WAV (“File menu > Export > Export as WAV”)

I presume that they have good reason for this format?
Generally, if a smaller file is required, it’s better to use a compressed format such as MP3 or OGG rather than reducing the sample rate to 8000, but perhaps they have a reason.