I cannot find the Opera repository. I tried
sudo aptitude install opera
sudo aptitude install opera-stable
sudo aptitude install opera-browser
but could not discover any repository.
The Opera website offers no help at all beyond downloading the .deb file for installation.
Gdebi does not post an error message, it simply crashes.
On closer examination, Gdebi says four packages must be uninstalled and libcurl3 installed. I manually removed the offending four and installed libcurl3, but Gdebi still crashes instead of installing Opera stable.