Kobo's ereaders support fixed layout epub3 ebooks but you will need to have them on the ereader as filename.kepub.epub for newer firmware and filename.fxl.kepub.epub for older firmware. See Kobolabs on Github at
Fixed Layout (FXL) Support. The issue I find with FLO epubs is much the same as with PDF in that if you don't have a large enough screen, the text is too small to view if the epub was not designed for a smaller screen device.