Google is now blocking the popular Linux browsers named Konqueror, Falkon, and Qutebrowser from logging into Google services because they may not be secure. It is not known when Google started blocking these browsers, but a user discovered this ban yesterday and posted about it on Reddit. Some users have reported that they could still login with Falkon [1, 2]. Google has not responded to requests to explain why these browsers are being blocked but have not received a response as of yet. Some people offer a variety of theories for why this is happening including it being an A/B test being done by Google.
Source: https://www.bleepingcomputer.com/news/google/google-now-bans-some-linux-web-browsers-from-their-services/