It's literally replacing every single swiped word with the "soft n-word." Every word, including things like "the" and "top".
This is happening to me right now on gboard, most updated version of Android, running on a Pixel 5. This has happened before and y'all gotta take my word for it that I haven't done anything to teach my phone that that's what I want to type.
If you hold down on a suggestion a trash can appears and you can remove it
It wasn't appearing as a suggestion, it was auto-replacing everything I typed. But only when I used the "swipe" input mode.