Using Whatsapp web
How to change the agent string to use Whatsapp Web? https://web.whatsapp.com
better use telegram web. Much more useful and safer (not US based). Works with every browser
That's no answer on how to use whatsapp web.
Agree, it's an excellent answer as it offers more privacy and a website that doesn't make use of the idiot technique of user-agent checking.
Aside, if you still want to use that crap, only installing an extension for user-agent.
No, it's not a good answer. I also preffer telegram over whatsapp, but I'm nobody to judge personal preferences, even if he misses the crappy MS Messenger.
To answer the question, try this extension to change the user agent. https://chrome.google.com/webstore/detail/user-agent-switcher/ffhkkpnppgnfaobgihpdblnhmmbodake
It still will tell you that you need other version but you can manually add the string you need. Look for them here: http://useragentstring.com/pages/useragentstring.php