That would just result in projects being flooded with low quality submissions by students who don’t care but are forced to do it. And who get angry when you don’t merge it since they need you to for their course.
Also, I totally ban using LLM, and unmotivated students often choose to work on very simple issues like easy refactoring or cosmetic aspects of web projects. It's okay with me for two reasons: first because it filters out unmotivated students from working of important issues and giving useless review work to open source maintainers, but also because we have all the other courses to do complex projects, here the point is to teach them by practice the workflow of contributing to an actual project, discussing with actual people, etc.
For some students it's already a good thing to have been able to get a copy of the latest development version of a given project, to install all of its development dependencies and tools, to compile it, and to reproduce the bug they chose to work on. It's not enough to pass the course, but it's a necessary first step to contribute to any project and it's quite a different experience from what they're used to with small school projects that are designed for teaching or that they entirely wrote themselves.