Hi Stiller,
I created a new thread from your post, it’s basically another issue than the one that was discussed in its original thread, and this way more people may read and help you out.
I’m not sure, but it does indeed seem as if SwiftKey at least is strongly intertwined with Google, so not having a Google account might well be the reason. Sadly there seem to be very few open source keyboards out there, but maybe other users will know.
It’s an alternative keyboard, multi-language, multi-features and capable of swipe too, of course. Moreover you can download addictional language packs.
Hoping to have been helpful…