Is there any working Whatsapp client for Ubuntu?

You can also just create a Chrome launcher for Whatsapp Web like this:

1. Use Chrome browser to go to https://web.whatsapp.com and follow the instructions to connect your phone.

2. Go to Chrome settings ⇒ More tools ⇒ Create shortcut. Check "Open as window" and press "Create". This will create a desktop launcher to Whatsapp web that opens in its own window. Allow desktop notifications (if needed).

And that's it! I assume this workaround works for Chromium as well, but haven't tried it yet.

PS.This method works also for Google Calendar, Google Keep and such tools for which there is no (official) linux client available.

I don't use any Whatsapp client on Ubuntu, but from my computer I use Whatsapp web:

https://web.whatsapp.com

You'll have to keep your phone connected, but Windows and Mac clients have the same constraint. And it's an official Whatsapp web site meaning as trustable as Whatsapp phone app. There are plenty of Firefox extensions that work with it.

There is also whatsdesk, an unofficial client for Ubuntu. It appears in KDE Discover results when "Whatsapp" is searched, so you can probably have a look into your software center to. You can also install it with:

sudo snap install whatsdesk

But I have never tested it and it's unofficial, so I would look for users feedback first...

Following this article, I tried up Rambox on my Mint installation. Works perfectly with Whatsapp so far. It has a free edition (like Franz) but doesn't have the annoying ads that block the app for 10 seconds every few hours.