You might find offline manga reading options on dedicated e-readers like Kindle or Kobo. Some manga publishers also release digital editions that can be downloaded for offline viewing. Also, check if your local library has digital manga collections available for borrowing offline.
I wouldn't recommend looking for free offline manga as it's often illegal and against copyright laws. But you can check out some legal platforms that offer free trials or discounted subscriptions.
Some apps offer a limited selection of manga for free offline reading. But it's not easy to find reliable ones. You might have to search and see which ones have the manga you want and are legal.
In most cases, it's not allowed. Crunchyroll is designed for online streaming to protect copyright and ensure a consistent user experience. Downloading for offline reading would violate their terms of service.