If you are using the Snap version of Opera, you can install the deb version by downloading the deb file from Opera or by manually adding the Opera repository.
I recommend uninstalling the Snap version of Opera before you begin. Backup any personal data or take note of any settings as the will not transfer to the deb version of Opera.
Method 1:
First, download the deb file directly from Opera by clicking the download button on the Opera webpage.
You will then need to copy that deb file to your user's ~/Downloads directory (the downloads directory in your file browser [like Nautilus] and not the downloads directory for your web browser if you are using a snap).
Once the file is copied to your user's ~/Downloads directory. Run the following command to install the file.
sudo apt install ~/Downloads/opera*.deb
Installing this deb file should automatically install the Opera repository and the stable branch of Opera.
Method 2:
Alternatively, you can manually install the Opera repository and then install the deb version using apt.
First, run the following command to add the key needed to verify the repository:
wget -O - http://deb.opera.com/archive.key | sudo apt-key add -
Then, run the following command to add the repository:
sudo sh -c 'echo "deb http://deb.opera.com/opera-stable/ stable non-free" >> /etc/apt/sources.list.d/opera.list'
Finally, run the following commands to install opera-stable:
sudo apt update
sudo apt install opera-stable
According to this Packages file, there should be no snap dependencies.
