Also you can use https://web.telegram.org as GNOME Web application. It supports desktop notifications.
- Go to https://web.telegram.org via Web (Epiphany browser)
- Click Install Site as Web Application…
- Confirm and wait a few sec, the application will be installed as GNOME Web Application
https://help.gnome.org/users/epiphany/stable/browse-webapps.html.en
