One useful measure for security through obscurity might be running on a platform that doesn’t have a lot of out-of-the-box exploits available for it. GEF supports x86, ARM, AARCH64, MIPS, PowerPC, and SPARC, but GDB also supports ARC, MicroBlaze, m68k, NDS32, Nios II, S/390, and TMS320C6x; of these, m68k is pretty comfortable and has a lot of tooling available, so might be a good choice.
The J1A or RISC-V might also be pretty reasonable platforms, but a bit bleeding-edge.
Linux on m68k seems to be pretty dead (web page not updated since 2000; last Debian release Etch) and FreeBSD is gone too, but NetBSD still supports m68k. Also HP-PA, SuperH, and VAX. These are “Tier II” ports. There are a number of JIT 68000 emulators for popular machines; Basilisk II (GPL) successfully runs old versions of MacOS, and there’s a reasonable amount of interest in QEMU support for it; QEMU at one point in 2014 got to being able to boot Linux/m68k on an emulated Mac, barely. These unfortunately require Macintosh ROMs.
GCC also, crucially, supports m68k, up to at least GCC 4.9 and maybe GCC 5, I’m not sure.
(Unicorn also, unfortunately, supports m68k.)