pizzadequeso I was also desperately looking for a FLOSS keyboard which could match Gboard in terms of UI friendliness and smartness. Esp. the autocorrect and smart word recommendations I found so smooth, Gboard often knows exactly how the rest of your sentence is supposed to go after a few words. Haven't found a keyboard quite as smooth. However, ASK (AnySoftKeyboard) comes close. It has very good recommendations and autocorrect for many languages. It actually has more personalization options than GBoard. For instance, you can extend the keyboard to more symbols by using gestures and holding buttons. You can also choose amongst many different layouts. It's truly a great alternative, you should try it.
I did not want Google to fingerprint me by tracking my typing patterns and language choice. I am not sure if Gboard does that. But didn't want to take that risk. Typing pattern is a very strong identity signature and language choice is a strong indicator for automated personality analysis. It is a very strong profiling tool for their extraction economy.