I have exported from InDesign as InDesign Markup (IDML) with extension .idml. These files open directly in Scribus version 1.5.2. What I am losing, however, is the ability to make fractions with OpenType fonts since Scribus appears NOT to do this. This is something I need to do since I work with a lot of dimensions such as: 5/16", 15/32", 61/64", etc. Where I see that I AM able to do this is in Affinity Designer! It works wonderfully – one page at a time… I wonder if Affinity Publisher will be able to open these InDesign Markup (IDML) files directly (as the open source Scribus can do) since I assume Affinity Publisher will include Affinity Designer's ability to work with OpenType fonts to make fractions.