Are there any modern "package manager" for C?
- Conan and vcpkg are probably the closest equivalent to other "language package managers" (e.g. Rust's cargo, or NodeJS's NPM).
- Spack is typically used in HPC/Scientific Computing domain.
- Nix (and Guix) are very powerful (system) package managers; these have enough nifty features that I'd call them "next-generation".
Probably also for sufficiently complicated projects, it may be worth mentioning sophisticated build tools like Bazel (which I think manages dependencies in its own way).
There is windows support now (in addition to linux and macOS), which I think was a roadblock for many, and we have gotten some very interest from folks outside the HPC community, e.g. Replica.one, who hope to use it for a software-defined OS for embedded devices: https://www.youtube.com/watch?v=sMxNafpDhng (skip to ~12min for some discussion of Spack, Nix, Guix, and portage)
Nobody wants a package manager for C in the C world. We want a package manager for whatever language we write our code in. A lot of C code is not a single C ecosystem, but coexists with other languages, even where it is all C we often have various code generation tools that look a lot like different languages that just happen to generate C, and sometimes we want to package the into for those tools not the C output.