A simple UIView that will move the contentView out of the way of the keyboard. It animates in sync with the keyboard and always works - even in a modal page sheet, a slide over, or any other context. Tested on iOS 12 and iOS 13.

KeyboardAwareContainerView.h

//  Created by Sean Heber on 9/26/19.
@import UIKit;

@interface KeyboardAwareContainerView : UIView
@property (nonatomic, readonly, nonnull) UIView *contentView;
@end

KeyboardAwareContainerView.m

//  Created by Sean Heber on 9/26/19.
#import "KeyboardAwareContainerView.h"

// keep the last known keyboard frame
// this is so that when a new container view is created while the keyboard is visible it can be correctly offset
static CGRect __keyboardFrame;

@implementation KeyboardAwareContainerView {
	NSLayoutConstraint *_constraint;
}

- (instancetype)initWithFrame:(CGRect)frame
{
	if ((self=[super initWithFrame:frame])) {
		_contentView = [[UIView alloc] initWithFrame:self.bounds];
		_contentView.translatesAutoresizingMaskIntoConstraints = NO;
		[self addSubview:_contentView];

		[_contentView.leftAnchor constraintEqualToAnchor:self.leftAnchor].active = YES;
		[_contentView.rightAnchor constraintEqualToAnchor:self.rightAnchor].active = YES;
		[_contentView.topAnchor constraintEqualToAnchor:self.topAnchor].active = YES;

		// we want to constrain the contentView to the bottom of the container view itself normally, but
		// the priority is set to one less than Required so that when the keyboard is visible, that
		// constraint will push it up away from the bottom edge if necessary.
		NSLayoutConstraint *bottom = [_contentView.bottomAnchor constraintEqualToAnchor:self.bottomAnchor];
		bottom.priority = UILayoutPriorityRequired - 1;
		bottom.active = YES;
		
		// monitor the keyboard's movements
		[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillChangeFrameNotification:) name:UIKeyboardWillChangeFrameNotification object:nil];
		[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHideNotification:) name:UIKeyboardWillHideNotification object:nil];
	}
	return self;
}

- (void)dealloc
{
	[[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)didMoveToWindow
{
	[super didMoveToWindow];
	
	// install the constraint that keeps the view above the keyboard
	_constraint = [self.window.bottomAnchor constraintGreaterThanOrEqualToAnchor:_contentView.bottomAnchor];
	_constraint.constant = self.keyboardBottomOffset;
	_constraint.active = YES;
}

- (CGFloat)keyboardBottomOffset
{
	// find the overlap of the keyboard with our window
	// NOTE: this assumes the window is never going to move while we're interested in this - probably a safe assumption on iOS, I think
	// NOTE: converting the keyboard's frame MUST be done directly with the screen's coordinateSpace - simply using fromWindow:nil does
	// not work correctly when the app is in side-over mode! (Probably a UIKit bug.)
	const CGRect windowRect = [self.window convertRect:__keyboardFrame fromCoordinateSpace:self.window.screen.coordinateSpace];
	const CGRect windowIntersection = CGRectIntersection(self.window.bounds, windowRect);
	return CGRectIsNull(windowIntersection) ? 0 : windowIntersection.size.height;
}

- (void)keyboardWillChangeFrameNotification:(NSNotification *)notification
{
    __keyboardFrame = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
	
	const NSTimeInterval animDuration = [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
	const NSUInteger curve = [notification.userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue]; // UIViewAnimationCurve
	const UIViewAnimationOptions animCurve = (curve << 16); // convert it to the options format
	
	// ensure we have a stable layout before adjusting the constraint so we don't animate things we didn't intend to
	[UIView performWithoutAnimation:^{
		[self layoutIfNeeded];
	}];

	// animate the change
	[UIView animateWithDuration:animDuration delay:0 options:animCurve animations:^{
		// update the constraint
		_constraint.active = YES;
		_constraint.constant = self.keyboardBottomOffset;
		
		// force the view to layout again - otherwise the change won't be animated the way we'd like
		[self layoutIfNeeded];
	} completion:nil];
}

- (void)keyboardWillHideNotification:(NSNotification *)notification
{
	// deactivate the constraint entirely so it doesn't interfere
	// NOTE: this prevents a problem when dismissing a modal view controller that still had a keyboard presented
	// in that case, iOS will dismiss the keyboard for you along with the dismiss animation, but if we don't
	// immediately disable the constraint, then while the keyboard is animating down along with the view, our
	// constraint would push the bottom of the contentView up - which looks terrible and is bad.
	_constraint.active = NO;
}

@end

This should be pretty easy to convert to Swift (or use as-is). Put your views in the contentView and/or make your constraints relative to it and this should take care of everything else. This also works fine for older codebases that aren't using auto layout, of course.