Man, I'm using heliboard and it has the same problems openboard had and the same problems gboard has with regard to autocorrect. And it's missing a lot of special characters, but I assume that's a work in progress.
You know what would really help the situation? You know how the spell checker underlines (or at least used to) incorrect words in red? It should underline corrected words in yellow or green or something. That way, when you're going over what you've typed, the autocorrected gibberish won't slip past you and will stand out. That would go a long way, but what would really improve it is if you could remove words from the dictionary that you don't use, and go back to however the system worked 6 years ago because it was pretty light on the frustration.