It depends. Some manga reader apps are legal if they have the proper licenses and permissions to offer the content. But many are not, as they violate copyright laws.
Mangatoon is worth trying. It has a decent collection and provides a smooth reading experience. Some of its features like bookmarks and recommendations are quite handy.
Tachiyomi could be what you're looking for. It's customizable and has a lot of sources for free manga. However, it might require a bit of setup to get it working just right.
Tachiyomi could be the one for you. It's customizable and supports multiple sources for manga. However, keep in mind that the availability of apps might vary depending on your region.
Mangatoon could be your choice. It has a user-friendly interface and regularly updates its manga library. However, the availability of specific manga might vary.