Didn't know it was available on pip.
Tried it but it boils down to the same issue: it tries to build it and thus I get the exact same error.
Did some more digging and I figured out it expects the limits.h to be in /usr/include.
It is not there of course, and I don't quite understand what does place those files there. I though kernel-headers would be the source but I guess those go in to the /usr/include/linux subfolder.
I think it comes down to missing part of the build toolchain (I'm more of a Debian user which has a package for that, and also a .net developer so the C/C++ tool chains is something I have avoided for many years now since I last used it. For this exact reason... dependencies, includes and libs).
I don't know if this exists, but would a solution be to find something like a slackware VM image that has all those things out of the box? A slackware dev box? And then build and copy the binary?
I don't know how your toolchain looks like for the stuff you make for unraid, but I guess this is something you run in to as well?
I agree with you on the whole Red Hat issue, they have been making dumb choices for a while now. Something to keep in mind down the line, especially considering Ansible is heavily supported by the community.
But Unraid is also not in the open source regard, I can get behind the paid license but it would be nice if the rest was more open to build your own and not be as restricted.