That's staggering that 50% are using LLMs. Have you tried making a statement in the job ad such as "in-person technical interview will be required for this position". Of course you may or may not choose to conduct the in-person interview in reality but the threat might cause the cheaters to self-select out.
We are a remote company, so that's probably not possible. Good point though in general.
We clearly state in the job posting, and at the start of the interview that we prohibit any AI use.