My favorite solution to this is to embrace the technology and have students really learn its uses and limitations.

Tell the students to prompt their LLM of choice to write an essay on a given topic or set of topics. Have the students include the prompt as well as the generated response. The actual assignment is for the students to then edit and critique the LLM-generated essay. This both requires them to demonstrate an actual expertise in the subject matter and directly shows them the limitations of LLMs.