> Linux
> Homebrew
> Arch Linux
> pacman -U jless
First, if you have to revert to homebrew as a package manager on gnu/linux you might as well tell the user to just use cargo directly, that way users only have to install the rust toolchain as opposed to the rust toolchain plus an alien package manger. The typical way would be to make cargo compile the thing, place in in ~/.local somewhere and add that path to PATH.
Second, "pacman -U ARG" installs from a file or from a URI. jless is neither. You have to properly package it before pacman will install from a file, which means you have to write a PKGBUILD file with some metadata and build instructions (about 20 lines) and call makepkg, which will then produce the package (a .tar.xz file if I'm not mistaken).
I suggest you first test the instructions you put on your website.