I am aware that people don't trust the Chinese. Which brands do you trust?

As another poster mentioned about the ReMarkable, the Boox works just fine offline. I do use mine online, e.g. for reading HN as I prefer the E-Ink screen for text. But as for note-taking, everything I do is offline, including moving the PDF documents to the desktop via ADB.

reMarkable tablet, for example, works offline just fine