Man, I've spent way too much time figuring this one out. So yeah, there are totally legal spots, but 'free' and 'complete' don't always go hand-in-hand, right? The biggest one is Webtoon, no question. They've got the official English releases for tons of big hits—'Lore Olympus,' 'True Beauty,' all that. The catch is you wait for daily passes or use the fast-pass system for the latest chapters, which can feel like a drip feed when you're binge-brained like me. I also check out Manta and Tapas regularly; they use a similar coin/free episode model. It's legal, it supports the creators, but the pacing requires patience.
For a more traditional manga feel, the Shonen Jump app is a monster deal. For like two bucks a month you get their whole vault, but they do offer the first few and latest chapters of series like 'One Piece' for free. I get my fix that way sometimes. Honestly, the ecosystem is built on freemium now—they give you a taste to hook you, which is smart, I guess. Just gotta manage that 'gotta read it now' impulse.