Include sources from subdirectories: target_sources or object library?

Personally, I treat object libraries as a last resort option. In most cases, static libraries are simpler and are better understood by developers. For specific situations where you have a clear use case that requires object files rather than static libraries, they may make sense, but it is not lost on me that it is an area that has been disproportionally represented in user questions compared to other parts of CMake.