I seem to be having an issue with an application that is almost definitely related to this multiarch situation. The application in question is Steam. Aptitude successfully pulls down Steam and a number of (i386) packages that it has as dependencies. However, many Steam games use OpenGL. At startup Steam complains that my video card is not using GLX direct rendering. The fix for this that I obtained from a debian forum is to install libgl1-fglrx-glx:i386. This does make steam stop complaining, however, it breaks Cinnamon. After installing that package, strange behavior such as new windows refusing to open begins to occur, and when I reboot I am no longer sent straight into graphical mode. Attempting to run startx produces errors (related to glx, of course). Purging the libgl1-fglrx:i386 package fixes everything (except that I'm back to being unable to run any OpenGL games from Steam).
How can I fix this so that the two OpenGL libraries can co-exist peacefully? More importantly, is this a bug? It seems to me that there should not be any packages that upon being installed will break your system. Yet the mere installation of libgl1-fglrx:i386 does just that.
Some details about my setup that may be relevant:
1. I am running the proprietary fglrx driver from AMD/ATI with a X configuration created with that driver's setup utilities.
Other details that probably aren't relevant but someone might find useful:
1. 3.11-2-amd64 #1 SMP Debian 3.11.8-1 (2013-11-13) x86_64 GNU/Linux (relevant output of uname -a)
2. Installed from LMDE201403 Cinammon Edition
3. My video card is a Radeon R9 270