m0n0wall is supported only on the x86 architecture. The types of devices supported range from standard PC's to a variety of embedded devices. It is targeted at embedded x86-based PCs.

This excludes non-x86 devices like the MIPS-based Linksys devices, ARM-based D-Link devices, etc. FreeBSD does not support the MIPS or ARM platforms. For a list of FreeBSD supported platforms, see this page. Some shown there are not yet functional (like MIPS, for example). The only platform supported by m0n0wall at this point is x86.