There isn’t really any debate about “Y” - it acts as a vowel in most cases, and as a consonant in some cases, particularly at the beginning of a word, as in “Youtube”. The “you” sound is a consonant sound, and that also answers the ukulele question: it’s “a ukelele”, because it’s the sound that matters here.

Using a more familiar example might help illustrate this: we say “a user”, not “a user”; similarly, it’s “a European”, not “an European”.

Here’s a good article about it: https://phonicshero.com/when-is-a-consonant-a-vowel-and-why/