It's not actually illegal as far as I'm aware, however it's not recommended: https://www.tomfowlerlaw.com/post/illegal-to-drive-with-interior-lights

Is it Illegal to Drive with Interior Lights On?

Generally, most states don’t have laws that explicitly say that it’s not legal to drive such vehicles with dome interior lights on.

U.K. goes a little further as an officer can judge it to be a distraction … but they can only tell you to turn it off, or it can count as contributing towards distracted driving but can’t be the sole reason.