Copy text to the clipboard shouldn't be hard. It shouldn't require dozens of steps to configure or hundreds of KBs to load. But most of all, it shouldn't depend on Flash or any bloated framework. That's why clipboard.js exists.
Y. Eshel, O. Levi, H. Roitman, and A. Nus. Proceedings of the 44th International ACM SIGIR Conference on Research and Development in Information Retrieval, ACM, (July 2021)