In iOS' Settings you can specify your preference to use bold text. This can be checked in code in a couple ways:
1. isBoldTextEnabled in UIAccessibility: https://developer.apple.com/documentation/uikit/uiaccessibility/isboldtextenabled
2. legibilityWeight from UITraitCollection: https://developer.apple.com/documentation/uikit/uitraitcollection/legibilityweight
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Creating UIAccessibilityElements, combined with a semanticGroup accessibilityContainerType, can also help you make components as complex as charts accessible. Example from "Bring Accessibility to Charts" WWDC21: https://developer.apple.com/videos/play/wwdc2021/10122/
If the user has Bold Text enabled, it will just work if you are using fonts based on text styles. If you have your own styles, or you are using a non-system font, you'll need to provide the bolder version of the font when the setting is on.
With accessibilityRepresentation(representation:), you can create a custom component and it can be perceived by assistive technologies as the view you pass as representation. No need to manually configure accessibility attributes. It is one of the most interesting additions to SwiftUI to help you develop accessible UI components. If your custom component behaves similarly to a native one, this is the way to go. https://developer.apple.com/documentation/swiftui/view/accessibilityrepresentation(representation:)
