I fail to see how the package management in a Linux distribution could be considered a walled garden. Commonly it's cited as the exact opposite of that (see the table here: [1]). What type of freedom are you missing in something like Debian, where you can edit and recompile the core components of your system at a whim, the system even supporting you through source packages, and where anything outside the package management is just a "git clone" and a compilation away? I really don't know what more anyone could ask for. Certainly we don't want to go back to the 90s way of downloading unsigned .exe files from some random guy's web site and then going hunting for matching DLLs?

[1] https://en.wikipedia.org/wiki/Closed_platform