Apport-retrace recombines an Apport crash report (either a file or a Launchpad bug) and debug symbol packages (.ddebs) into fully symbolic stack traces. This can optionally use a sandbox for installing debug symbol packages and doing the processing, so that entire process of retracing crashes can happen with normal user privileges without changing the system.

You need to install gdb-multiarch if you want to be able to retrace crash reports which happened on a different architecture than the one you run apport-retrace on.