We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
epub problem galaxy S6
Hello from Sweden
I have a problem for you to solve.
I have created a few epub-files in order to learn the way it functions. I use Sigil to create them directly, but I have also used MS.word and calibre.
They all behave in the same strange way:
When I download the file to my desktop it works just fine.
But when I download into my galaxy s6 the file extension becomes .txt, and of course the file cant be read by an ebook reader.
Please try this link and see for yourself:
Looking forward to your wisdom!