I’ve had little trouble with Opera on Linux, but if you do, perhaps this information will help.
VIEWING DEBUGGING MESSAGES
You can launch Opera from a command line and view error messages as they are generated. Optionally, you can export any appropriate environment variables first. For example, to debug a problem with the Flash plugin, the following sets an appropriate level of plugin-related debug output, then launches Opera, going straight to a Flash test page:
$ export OPERA_PLUGINWRAPPER_DEBUG=7 $ opera http://www.adobe.com/software/flash/about/
Opera-specific plugins go in /usr/lib/opera/plugins/, and plugins shared with other browsers go in /usr/lib/mozilla/plugins/. In practice, plugins are almost always in the latter. In either location, plugins are typically owned by root and have permissions of 644.
When Opera does not see a plugin in /usr/lib/mozilla/plugins/, it is often suggested to place a symbolic link to it in /usr/lib/opera/plugins/, though of course in a properly working installation this should not be necessary.
If you make manual changes to either of these directories, restart Opera.
SETTING FILE ASSOCIATIONS
Opera attempts to learn file associations as needed by presenting the user with pop-up dialogs, and this usually works. Occasionally it fails, however, and I have to set an association manually. Associating magnet links with a preferred BitTorrent client seems to be particularly prone to this problem.
Opera Software operates a number of Usenet groups and web forums. I find a greater number of answers on web forums but better answers on Usenet, so I usually begin my search on Usenet.
On Usenet, Opera Software sponsors the opera.* tree of groups in which their employees actively participate. Choose the one most appropriate for your issue; I most often use opera.linux and opera.general.
Use the Opera bug report wizard.