Nokia N9 already has a built-in internet browser. It’s not the best, but it works. I like having some browsers for my Nokia N9, and currently I have Firefox Mobile and Opera Mobile installed. Both browsers (Firefox Mobile and Opera Mobile) are not available from Ovi Store. If you’re using Symbian for your Nokia, you can download Opera Mini. Firefox is not yet supported.
I’m not considering the installation process as something difficult. Yes, it’s not like the regular installation procedures. It’s my first-time experience too. So far, everything works without any issue at the moment. For Opera Mobile installation, I just follow the installation tutorial from Nokia N9 Fans Club. It’s an unofficial site, not maintained by Nokia.

Now, let me share a bit about how I installed Opera Mobile. Anyway, my N9 is running MeeGo 1.2 Harmattan with software version PR1.1 (20.2011.40-2_PR_005). And, if you’re not familiar with command line, you can continue reading.

Installation

First, you need to turn Developer mode on by going to “Settings” > “Security” > “Developer mode”. I have done something in Developer mode when I fixed the Twitter app issue about two weeks ago. Don’t worry, it’s safe. :)
Since it’s not officially supported by Opera, you need to download from another source. I downloaded the installation file from My-Meego.com website. You can download directly from your N9 browser, or  from your laptop/PC and transfer it to your phone. I downloaded directly from my phone. It’s around 12 MB.
So, where’s the file? You can find it under /home/user/MyDocs/Downloads/. Its file name is: operamobile_11.11.00-1_armel.deb. It might be different when the new release is available. You can check using application like File Manager or Filebox. You can not install it directly by double-tapping (or opening) the file.

Go to Application screen and open Terminal. You need to work as “root” to get permission to install. By default you’re logged-in as “user”. On the Terminal screen, type “devel-su” (without quotes) and press the Enter button. You will be asked for a password. The default password is “rootme” (without quotes), and press Enter button again.
Great, you’re now working as “root”. (See screenshot)
You need to your Download folder by typing: cd /home/user/MyDocs/Download/ on your Terminal screen, and hit the Enter button.
If you want to see list of files in the directory, just run ls -l and you should see operamobile_11.11.00-1_armel.deb there.
You are ready to install it now.
Type this command: dpkg -i operamobile_11.11.00-1_armel.deb and hit the Enter button. If you’re too lazy to write down the file name, just type dpkg -i opera and hit the “Tab” button there to complete the file name. The installation process only took few  seconds.
When it’s done, you can close the Terminal by typing exit or swiping the screen down. Easy.

Other notes

About your User Agent, it will be detected as: “Opera/9.80 (linux armv71; Opera Mobi/10; U; en) Presto/2.7.81 Version/11.00”.
By having Opera Mobile installed, you can expect to have another browsing experience. Opera Mobile offers some great features. Go to Opera website for detailed features. It’s not yet officially available, but it’s running great. On Nokia N9, it only offers a landscape view — no portrait view. The menu button on the bottom right is a little bit not responsive. Sometime it’s slow to open. I tried to browse some websites, and I have a pleasant browsing experiment.