Support both orientations, if possible. I know not even iOS itself does it, but it hasn't always been like that. You'll create a more robust UI that will be easier to port to iPadOS. And especially, don't force your users to rotate their devices.

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When configuring a largeContentImage or adjustsImageSizeForAccessibilityContentSizeCategory, it is important to use a pdf asset and preserve the vector data so the icons are crisp at any size.

Hacks are accessibility’s worst enemy. An example. There is a ‘trick’ floating on the internet: if you want a button with an icon to the right of the text, set the semantic content attribute to force right to left. Great way to create focus traps.
Check isReduceTransparencyEnabled to lower transparency. A great example is Spotlight. Not only transparency is removed but it keeps the main color of the background, it feels personalized and contextual but reduces noise and improves contrast.