I just downloaded opera-stable_56.0.3051.99_amd64.deb
from https://www.opera.com/de/download
and ran
sudo dpkg -i opera-stable_56.0.3051.99_amd64.deb
It complained about some missing dependencies so I ran
sudo apt-get -f install
sudo apt install apt-transport-https
then reran
sudo dpkg -i opera-stable_56.0.3051.99_amd64.deb
anyway, am worried about what evil that has done to my otherwise clean debian distribution and how to undo it. At the least it has replaced the firefox which used to launch from the icon at the bottom of xfce with itself.
Actually, the command under the button is:
exo-open --launch WebBrowser %u
..so no opera keyword.
How do I get it back to how it was and if necessary clean up anything else bad which it might have done?