Disclaimer: I wrote this script for my own personal usage. It is not officially supported by Opera Software.
This script converts an Opera Debian package into standalone (portable) format. If you do not already have it, fetch it as follows:
git clone https://gist.github.com/8416e36372f1a976a713.git
Now use the script to convert an Opera package as follows:
sh standalone-opera.sh opera-developer_27.0.1670.0_amd64.deb