Before that, there was the case of ÿ and Ÿ in the base IBM character set (see https://en.wikipedia.org/wiki/Ÿ). The former exists in a handful of proper nouns in French and Hungarian (as in about five proper nouns), but only as a y with a diæresis, which would normally be handled with a Unicode modifier symbol. It is also used in a couple of endangered languages in South America, which would not have influenced the character getting in to a PC character set. It is thought that possibly it was supposed to represent the Dutch "ij" character, but apparently that is never written as "ÿ" in print. Ÿ seems to not be used by any language.
> Ÿ seems to not be used by any language.
Surely those aforementioned non-initial cases would sometimes find themselves in a piece of all-uppercase text? You'd have found such things in print media even before the advent of computers.
Not everything is upper/lower convertible like ß for example (as far as I know)
At least until 2017, I imagine there are others though.
> In 2017, the Council for German Orthography officially adopted a capital form ⟨ẞ⟩ as an acceptable variant, ending a long debate. https://en.wikipedia.org/wiki/%C3%9F
Great, so they added Ÿ but not n̈, making it very difficult to write music reviews.
(Not sure how the latter will render in your browser).