> [...] have letters that can't be capitalized (for example ß).

Here's ß capitalised: ẞ

Bad example, but you're otherwise correct. My personal pet peeve is systems mangling names with umlauts. Such names used to be common in my country, but they've become pretty rare now with globalisation likely to blame. But a workaround nowadays seems to be to give two different first names: one that has no special letters and another with.