Not OP, but consider using FUTO Keyboard. It’s made by the group Louis Rossmann works with, and it has offline speech to text (no sending data to Google), swipe keyboard, and completions. It’s also source-available, which isn’t as good as open source, but you could examine the code and verify their claims if you wanted to.
I’m using it and, while it’s not perfect, it’s way better than the open source Android keyboards with swiping that I’ve tried.