Facebook Messenger (the standalone desktop app was discontinued in 2020). However, you can still use it perfectly on PC via:

⚠️ Be careful: Third-party websites offering "Messenger for PC .exe" may contain malware. Only use official web methods.

If you want the app to feel like a standalone program but don't want to download a heavy installer, you can install it as a "Progressive Web App" (PWA).

Télécharger ou mettre à jour l'application Messenger - Facebook