What is the simplest way to get a rawhide i686 VM? I came across a
nasty architecture-specific bug, and the code investigation isn't of
much help. There is no obvious way to access a core dump via mock
(could you please ping me if it exists?) and the VM looks like a
reasonable choice.

https://rpm-software-management.github.io/mock/Plugin-ChrootScan

or

mock -r fedora-rawhide-i386 --no-cleanup-after foo.src.rpm

mock -r fedora-rawhide-i386 shell

   cd /builddir/build

Miroslav