@vrsdnl Since browsers don't send your location to sites (unless the sites ask for your geolocation and you allow it), it's probably just a matter of sites guessing your location wrongly.
You can try dragging the file onto the opera://extensions page.
If that doesn't work, extract the file with an unzip utility, goto the URL opera://extensions, turn on developer mode, click "load unpacked" and point it to the extensions folder that has manifest.json in it.
I found a solution to this. There's a chrome extension called Transparent Standalone images. Now this is a chrome extension but I added it to my OperaGX too. If you dont know how to add chrome extensions in Opera browsers, you can google it and find some videos on how to do it. Adding this extension and restarting the browser made PNG images with transparent background have transparent background in preview finally, 😁 YAY!!! Link to the extension : https://chrome.google.com/webstore/detail/transparent-standalone-im/inmelfailofaofnfdjdkljfchjhogbmh?hl=en