Double-check that other Chromium browsers like Chrome, Vivaldi, Brave, Chromium-based Edge, and plan Chromium still work correctly.
For Opera, download the Opera installer, launch it, click "options", set "install path" to a folder named "Opera Test" on your desktop, set "install for" to "standalone installation", uncheck "import data from default browser", and install. Test in that Opera, but do not enable any extensions and do not enable Opera Sync. Also, goto the URL opera://settings/batterySaver in that Opera, turn off the battery saver and restart that Opera. Test with standalone installations of Opera Beta and Opera Developer from https://www.opera.com/download too.
If things still don't work in those standalone installations, in them, goto the URL opera://gpu to see if there's any info in there that gives you a clue as to why Opera's not using your Nvidia GPU. Also, you can try going to the URL opera://flags/#ignore-gpu-blacklist. Enable the flag, restart Opera and try again. Also, try playing with opera://flags/#use-angle.
Are you running your laptop on battery or is it plugged in? Any difference?
If you search the net for a solution for Chrome, it might work for Opera too.