You may then point out that you don’t actually need the cross-compilation toolchain to exist in Docker proper. FOSS toolchains do exist for TILE, 32-bit PPC, MMIPS, SMIPS… Why can’t you use them to cross-compile binaries on your desktop machine and then use tools like [Buildah](https://buildah.io/) to copy those binaries into the image unchanged?

You can, but now you’ve bought several new problems:

1. Until someone actually does this and provides a compelling case to MikroTik that they should expend the effort to build `container.npk` for those old CPU designs, my sense of MikroTik’s public statements on this matter is that they have no interest in spending the engineering time. It not quite a classic chicken-and-egg situation, but without working images in hand, I don’t see a bid to make MikroTik append this task to its development pipeline succeeding.(^I base that interpretation on the hiss of radio silence I got in response to [this challenge](https://forum.mikrotik.com/viewtopic.php?t=204868#p1058351).)

2. It’s only “easy” for static binaries. If your program requires third-party shared libraries, you have to build them, too, along with the dynamic link loader, and… You’re likely to find yourself building a small Linux distribution as dependency leads to dependency, and now you're off on a major [yak-shaving](https://www.hanselman.com/blog/yak-shaving-defined-ill-get-that-done-as-soon-as-i-shave-this-yak) expedition.
2. It’s only “easy” for static binaries. If your program requires third-party shared libraries, you have to build them, too, along with the dynamic link loader, and… You’re likely to find yourself building a small Linux distribution as dependency leads to dependency, and now you're off on a major [yak-shaving](https://softwareengineering.stackexchange.com/q/388092/39162) expedition.

3. This plan ignores one of the most powerful ideas in the OCI container ecosphere: you don’t cross-compile programs at all, you boot a Linux distro image for the target platform under QEMU, then use the native tooling to produce “native” binaries. What this means in practice is that if you can assemble:

    * a sufficiently complete Linux distro ported to your target platform; _and_
    * a version of QEMU that will run it on your development system; _and_
    * the binfmt patches necessary to let your local kernel tie the two together…