There is a new application available for Sparkers: Caprine.

What is Caprine?

Elegant Facebook Messenger desktop app.

Caprine is an unofficial and privacy focused Facebook Messenger app with many useful features.

Installation (64 bit only):
apt update
apt install caprine

Caprine

The application is licensed under the MIT License.
The project’s GitHub repository: github.com/sindresorhus/caprine
The project developer is Sindre Sorhus.