A curious question: Would it be technically possible to detect city lights on other planets? NIRCam, NIRISS and NIRSpec cover only a small part of the visible light spectrum at all.

There's been a study! If you make a bunch of extreme assumptions (brilliant, narrow-band, fully exposed city lights covering the entire surface of the planet), then JWST might possibly, barely be able to detect a signal from Proxima b. www.centauri-dreams.org/2021/05/21/p...

That's a whole ball of wax. Starting with whoever put the city lights up have optic nerves that register the visible spectrum