@alexs77 @leocg
Yes, it worked! Thank you very much!

I had just one entry there and this was the first ever Opera browser on this computer, so it is kind of surprising how this happened. But I am super glad that it works now, logging in to all accounts (Google, Opera, Github, Gitlab and tons of others) every time I had to restart Opera or reboot the computer was supper annoying.

Thanks! This advice should make it to some official FAQ.