I'm on a new install of Lubuntu 12.04 on an Acer Aspire 5534 (specifications here, tl;dr: AMD dual-core 64bit) trying to install steam_latest.deb from the Steam website. When I open gdebi to install, it tells me that it's uninstallable because it's for a i386 architecture. I've tried installing ia32-libs (installed, no success), gdebi --add-architecture i386 (with and without --force, command unknown). This is all I've found to fix the problem, but none of it has worked for me. Any suggestions are welcome, thanks for your time.
Some similar questions have already been asked here.
The problem, in short, is trying to force the installation of a 32 bit package on a 64 bit machine.
I would suggest you to have a look at these questions: