The Opera browser is available for Linux again, albeit just in the developer stream for now.
The Norwegian browser maker used to have something for Linux until around the time, in early 2013, that it abandoned its own framework and rendering engine in favor of Chromium and WebKit. Pre-revamp version 12.x was the last with Linux support, and there is indeed an open-source project called Otter Browser that aims to recreate that version.
Now, probably to the surprise of some, Opera is back on the free operating system with the upcoming version 24. It's in the low-stability developer stream and right now it's only guaranteed to work on Ubuntu Linux 64-bit with the Unity or Gnome shell, but it's there.
As the Opera team said in a Monday blog post:
Many of us at Opera use Linux as our primary platform. It's great to be able to try out the newest developments of Opera on Linux once again. Adding Linux to our browser line fulfils an important part of Opera's vision to shape an open, connected world. We want everyone to have fast and safe access to the web. Adding Linux opens up that possibility to more machines running the open-source operating system.
The new Linux version of Opera 24 will be the first to take in features released for Windows and OS X versions last year, notably the Stash read-later facility and the Google Currents-ish Discover. Speed Dial (Opera's answer to bookmarks) and the data-compressing Opera Turbo feature have also seen heavy revamps during that period, so that's more for Linux Opera fans to look forward to.
Opera said it would look into other non-Ubuntu Linux platforms "as our development progresses".