"Insecure connection" warning on most of the websites including opera.com and youtube.com

[Sixtytrees]

Sixtytrees last edited by

Hi, I've changed some Android phone settings (XiaoMi). I don't remember which once I've changed, but it was a long list (some 20 enabled items) that I have turned off.
Now Opera shows "insecure connection" warning for 99% of the web sites, including opera.com and youtube.com

Firefox still works normally. I've reinstalled Opera, hoping to reset the settings to defaults, but the problem remains.

What could cause this behavior and how can I fix the issue?
Thank you