Just got motivated to try LyX, and it is fully functional on mobile!
This shows selecting items off the screen on the toolbar.
This shows that selecting a footnote via touch opens the footnote edit view.
This shows that outline view might not be too usable, but note that all the text on the right is fit to the visible area. Note: I had trouble clicking the upper right corner ‘x’, but could still easily close the outline from the toolbar view menu.