I tried it again, but to no avail. I set Location to both 'High accuracy' and 'Device only', but in both cases it did not work with Opera on more sites. When I tried the same with Brave, it worked flawlessly. And I have granted Opera access to location services. So there should be another thing which I have not enabled in Opera. I have enabled 'Desktop site' to prevent some websites showing limited WAP pages and disabled Data saver.