across architectures: you're right, as of now it's x86_64 only
across operating systems: it works on linux and freebsd as-is (thanks bakul), and with a few changes on windows+libc (thanks ktye) - https://github.com/ktye/i/tree/master/_/ngn though i personally never use windows
[1]: https://bitbucket.org/ngn/k/src/b54eb5cfea5eb821fe1de68d2a8a...