Unpack the installer, and locate the libflashplayer.so file

Install the 32 bit wrapper (linux32) and the package conversion tool (alien)

sudo apt-get install linux32 sudo apt-get install alien

sudo ln -s /usr/lib/nspluginwrapper/x86_64/npconfig /usr/bin/nspluginwrapper sudo alien -d nspluginwrapper*.rpm sudo dpkg -i nspluginwrapper*.deb sudo mkdir /usr/lib/mozilla/plugins32 sudo cp {path to}/libflashplayer.so /usr/lib/mozilla/plugins32 sudo nspluginwrapper -i /usr/lib/mozilla/plugins32/libflashplayer.so

sudo ln -s /usr/lib/mozilla/plugins/npwrapper.so /usr/lib/mozilla-firefox/plugins/ sudo ln -s /usr/lib/mozilla/plugins/npwrapper.libflashplayer.so /usr/lib/mozilla-firefox/plugins/

Unless some other tutorials you can read on the net, i made a special directory for the 32 bits plugins, because even if it doesn't make firefox explode, the fact that the 32bits plugin is in a directory checked on firefox startup raise and error telling that this plugin can't be loaded.

Appendix :

For those who don't understant i use a link in the /usr/lib/mozilla-firefox/plugins instead of installing the wrapper directly for Firefox (some pleople don't use Epiphany, and don't care about flash working for it), here is why :

nspluginwrapper force the nswrapper-libflashplayer.so to be created in /usr/lib/mozilla/plugins when you run "nspluginwrapper -i".