I spent ages trying to figure this out myself, honestly, and the biggest problem is separating the fan translations from the official releases. So many people want that quick fix, but I'd say you're way better off using the preview functions on legal platforms. For example, BookWalker lets you read a sample of most books, sometimes the first 20-30 pages, which is often a full chapter. Same with Google Play Books and the Kindle store. The samples are there to hook you, and honestly, for a lot of series, that first chapter is all you need to decide if you want to commit. Relying on random aggregator sites is a mess—you'll get broken image links, machine-translated garbage, or stories that just stop updating halfway through because the fan translator got a DMCA notice. I've had that happen more times than I care to admit.
A decent alternative for ongoing stuff is to follow the official publisher's serialization on sites like KADOKAWA's ComicWalker or Manga-Up! They sometimes serialize light novel chapters weekly as part of a promotion. It's not the whole book, but it's steady, legal, and free. The real trick is shifting your mindset from 'where can I download the whole thing' to 'where can I follow this story officially.' If you find a series you love, getting the first volume cheap on Amazon or subscribing to something like J-Novel Club's membership (they have free previews for members) isn't a huge ask. The fan translation scene has really dried up for popular stuff anyway.