Janet built with 32-bit pointers saved about 20 percent of its memory and lost 50 percent of its speed; the x32 ABI would keep the cache win without that cost, but Arch doesn't compile it in and Debian ships it disabled.
A firmware dump plus the debug port's identity register name the chip in Ubiquiti's USW Flex Mini, and Zephyr's thin support for it is what blocks a fresh firmware.
A long-standing Rockbox TODO closes: someone swept an undocumented iPod chip's mode register through all 256 values and wrote the missing remote-button driver.