Some ideas for ports to OS kernels:
Debian GNU/Any Xnu Plan9 Haiku ReactOS ?OpenSolaris MenuetOS seL4 Genode OS Minix 3 Redox Plan 9 Akaros Minoca ToaruOS Fuchsia
Some ideas for ports to hardware:
LM32 RISC-V/lowRISC Elbrus E2K ETRAX CRIS (cris-linux-gnu) TILE-Gx (tilegx-linux-gnu) Epiphany more
Some ideas for ports to software defined architectures:
CloudABI WebAssembly Apple Bitcode LLVM IR