Hold on, do you not see the insane contradiction of not wanting to rely on having cargo installed but requiring something is deployable and tested in a docker container? What?!
A very easy way to do this (for me anyways) is using a Docker container. I use this method to test all of my documented commands. But there are other ways, of course, like using a clean VM. Regardless, just test the commands without assuming the customized state of your own workstation!
The point is that if I follow the hypothetical instructions of running "cargo install something", the result will probably be "cargo: command not found". When you test this in a clean system and find this error message, this places on you the burden of depending on Cargo, so the least you should do is to make sure "cargo" will work for the user who is reading your docs. At a minimum, you should link to somewhere that explains how to install Cargo.
tldr: you should make sure your instructions work as-is from a clean installation of your intended distro(s), regardless of how you prefer to do so.
Yet I got confused the first time ever some README told me to run "npm install blah". WTF is NPM? I didn't care, really, I just wanted to use blah. Conversely, later I worked with Node devs who would not know where to even start if I asked them to install a C++ toolchain.
The point is don't assume too much about the background of the people reading your instructions. They don't have in their heads the same stuff you take for granted.
I've found instances where some documentation instructions pointed to run Maven, and the commands worked in their machine because Maven is highly dependent on customizations and local cache. But it failed in other machines that didn't have this parameter configured, or that package version cached locally. And trust me, Maven can be _very_ obtuse and hard to troubleshoot, too much implicit magic happening.
Testing in a clean container or VM would have raised those issues before the readme was written and published. Hence my point stands, testing commands in a clean system is akin to testing a web page in a private tab, to prevent any previous local state polluting the test.
Frankly I prefer the 10,000 approach suggested by XKCD: https://xkcd.com/1053/