Free Chess Club is a modern interface for the Free Internet Chess Server (FICS) — one of the oldest internet chess servers with over 800,000 registered accounts.
You can try out the interface here: Free Chess Club.
In addition to the hosted web interface, there are cross-platform Electron-based desktop apps (under Releases) and Capacitor-based mobile apps that you can access from the mobile app stores.
To get started locally, just type:
$ yarn start
and point your browser to http://localhost:8080