I tested the official Seafile demo (7.0.2) with my mobile (Android 8.1) and Firefox. The UI is not very mobile friendly. The menu is covering all the screen. Clicking on any menu item does not give any result. When writing a Markdown document, letters or whole words are duplicated.
There is a warning, though, one is supposed to use Chrome. But as a good Open Source product, shouldn’t Seafile be cross-browser compatible and not be tied to a specific browser?
(Other than that I am a happy Seafile user. Keep up the good work!)