TNR works, as feral cats often cannot be adopted past a certain age, they just won’t let humans near them willingly. But there isn’t a need to kill cats for not wanting to be adopted, they can be fed and over time their population can be dramatically reduced, it just requires actual commitment to the program and free access to spay and neutering services to the public.
Have you tried a harness? Some cats that demand to be outside seem to be satiated with walks. Can take a while to normalize the harness with them, though.