I have a D01100 its a gen4 (my mistake). I just plug it into my computer or phone and transfer an epub right onto it. I never hooked it to an account. I even have a program to convert Manga but it’s been awhile since I did that and I honestly can’t even remember the name of the program or how it works. Had this thing since 07 so…
I google the book I want to read with “epub”, download the file, plug my phone directly into my Kindle and use the file system just like I used to on a PC. Never really had to do much more than that.
I’m not really sure. I’m fairly sure the fire is locked down to not let you do this kind of stuff but I have two gen4 and have never bought another.