I don’t have a firestick, but they might just be meaning a different launcher. I use this one on a Shield. Works great. https://www.firesticktricks.com/wolf-launcher.html
Pretty sure it’s Wolf Launcher - Install guide here at troypoint
I have so much trouble getting DRM free epubs on to a Kobo. I can transfer the files easily enough (Kobo is sadly lacking an email to device option though) but then once I start reading them, the page turn gets gradually slower and then eventually the device freezes… Doesn’t seem to matter whether the are EPUB or kpub.
Got excited there for a moment…but 2025 !?.. C’mon man