Thank you for sharing! 
I took a quick look at you’re workaround , apparently you went the route of hardcoding the sizes of all possible different keyboardsizes?
When they disable auto suggestion though the keyboard changes size, how does it cope with that?
Didn’t know the crowd using iOS 12 was that low ? Are you sure about only 5% remaining with iOS 12 and lower? In that case it might be a waste of time to focus on that particular issue.