"Browser or app may not be secure. Try using a different browser." error with Flutter Firebase Google Login

Incomplete answer:

This problem isn't specific to flutter. It happens whenever you try to sign in to Google in a Chrome instance that has debugging turned on. In other words, if you, your automation software, or IDE starts up chrome with a command like chrome.exe --remote-debugging-port=9222

If running Chrome normally (out of debug mode) is not an option, then try https://support.google.com/accounts/thread/22873505?msgid=24501976 or if you are using Electron then try https://support.google.com/accounts/thread/22873505?msgid=24503570 but I, personally, haven't been able to make these work for me, yet.

Please upvote the question at https://support.google.com/accounts/thread/25209002 if you want a solution to this problem that actually works.

The issue was with the chrome developer version Flutter use to launch as a device. If we open the same URL (localhost:portnumber) in the normal chrome, it will work without any issue.