There are a few websites that claim to offer free light novels, but many of them might have copyright issues. It's best to look for authorized platforms that offer free trials or limited free content.
Some public domain websites offer free light novels. However, the selection might be limited and the reading experience could vary. Also, make sure to check the legality of the source.
I know that Project Gutenberg sometimes has light novels available for free. Another option could be websites of independent authors who offer their works for free. Just remember to be cautious about the legality and quality of the content.