The German capital sharp S letter was introduced recently as part of Unicode in 2008.

When this character appears in a Text component, using a font that does not contain the character, the fallback behavior on an iOS device works in iOS 8.4.1 and iOS 9, and the character is displayed via a system font without issue.

But on a device running iOS 10 or 11, it instead shows a [?] character (question mark inside a square), even in Unity 2017.1. iOS 10.3.3 itself has no trouble displaying the character in Messages, Notes or Safari so the character clearly exists in a system font.

Steps:
1. Build and Run attached project ("GermanFont.zip") on iOS10 or iOS11 device

Result: German upper case letter sharp S (ß) does not fall back ([?] is shown).

Reproduced with: 2017.3.0a7, 2017.2.0b11, 2017.1.1p2, 2, 5.6.3p2.

iPhone SE | iOS9.3 | not reproduced
iPod 6th gen | iOS10.2.1 | reproduced
iPad mini 4 | iOS11.0 | reproduced

Note: not reproducible on Android.