I did not reset all my settings, but created a new user and started brave for the first time. This browser window did not have any problem linking whatsapp.
Ubuntu Unity 22.04, Brave [Version 1.40.113 Chromium: 103.0.5060.114 (Official Build) unknown (64-bit)]
So it must be a setting or an extension.
Then I disabled all my extensions, and my main brave browser started to wok.
This is what worked for me alltogether:
- Disabled secure dns
- Turned off shield for web.whatsapp.com
- Disabled all extensions.
After this I was able to link the device and whatsapp started to work.