As a library author you basically have to wait for distributions to start shipping it, or make users manually install dependencies (and then make the build work with libraries installed into /usr/local).
That's assuming the distro even does package it up. Because beyond Archlinux packaging, packaging up a DEB is painful. RPM is somewhat less painful, but you still need to contend with N distros. Your lib depends on lets say 4 other libraries, perhaps some of the GTK ecosystem of libraries. Good Luck!
When you go to build C projects, there's usually a long list of instructions, per distro/os to set the environment up correctly.
Compare that to a Rust project where you git clone and cargo build to get going. No instructions needed, no insanely complicated esoteric m4 macro system, or ad-hoc programming language (looking at you CMake), and snowflake package manager needed.
Meson is the only C/C++ build tool I know of that solves the issue of building complex C/C++ programs with dependencies sanely. Especially in the case where both your application and your dependencies are unreleased as of yet, as is the case with Gnome and KDE applications as they are developed.
Shudder
Or even plain old tarball with any sort of build script.
And vcpkg, cargo are already good options for those that need cross-os package manager.
It's a symptom of the tooling that this is even a thing.