Don’t assume it’s safe to use pre-built dependencies when compiling C++ programs. You might want to build from source, especially if you can’t determine how a pre-built object was compiled, or if you want to use a different C++ standard than was used to compile it.
Ubuntu has public build logs which can help you determine if you can use a pre-built object, or if you should compile from source.
pkg-config is useful for generating the flags needed to compile a complex third-party dependency. CMake’s PkgConfig module can make it easy to integrate a dep into your build system.
Use CMake IMPORTED targets (e.g. BZip2::Bzip2) versus legacy variables (e.g. BZIP2_INCLUDE_DIRS and BZIP2_LIBRARIES).