On my S8 keyboard the configuration menu can be opened using the gear icon appearing in the keyboard. In the configuration menu there should be a bunch of options under "Smart typing" including 'Predictive text' which can be turned off.
This is in the european market, though, I don't know if it's configured differently for different markets.
Here's the problem. I already turned off all those options long ago, but the annoying behavior remains. To be clear, I don't mind the keyboard predicting things. It's only the retroactive changes that bother me.
Someone else suggested Swift keyboard, so I'm going to give that a try.
This is in the european market, though, I don't know if it's configured differently for different markets.
On google the query "samsung turn off keyboard autocorrect" provides links such as https://www.androidcentral.com/how-turn-and-autocorrect-sams... which may or may not be relevant to you.