Is it possible to use Polylino on Chromebook?

It is possible to use Polylino's web version, app.polylino.co.uk with your Chromebook. But you can also download the app if your Chromebook supports Android apps. Search for the app in the Google Play store on your Chromebook.

In this list you can see which models will support Android apps from Google Play:

https://www.chromium.org/chromium-os/chrome-os-systems-supporting-android-apps

Sometimes it may be necessary to first activate Google Play on the device.