kyoo-kyoom-ber?
Acutally I think that’s not quite right. The original English long and short U would have been [u:] and [u] as in sunu (son) and sunne (sun). I don’t know when the [ʊ] (foot) vowel entered English.
And then you run into accents. For me, debut sounds differently from all the other examples, which all sound alike.
These all rime to me.
Of course – they all end in “oot”.
Which are all the “short u” sound, and are therefore irrelevant.
They’re covered in ice?
See the first sentence of the OP.
Ditto.
It’s different to me as well but only in that the “t” is silent. The “u” is the same. How do you pronounce it?
It’s got a much longer sound to me. All the other examples you gave in your OP have the same sound, shorter.
That’ll teach me to post at 2 in the morning. The Wikipedia article I linked should answer at least your first question, though.
For me duke, nuke, tube do have the ‘y’ sound; it depends on your dialect.
Also ‘due’. I was sooooo confused at first when I saw Americans on the internet mixing up due and do.
Similarly, for me “Stewart” and “Stuart” are pronounced differently.
When I say “Stewart”, my lips are narrowed. For “Stuart”, my lips are more puckered.
The better question is “why is [insert word] spelled this way?”.
The pronunciation of a word precedes its spelling. English orthography is extremely conservative. Spellings often fossilize a pronunciation at some particular point in time. This is why in spelling bees, the contestants may ask for word origin.
For example, “beauty” is spelled that way because the French spelled it with a “eau” when we took the word from them. Linguists can often deduce how French (or a specific dialect of French) pronounced a word by noting when and where English took the word and how it was spelled and pronounced by the English. Sometimes we stole the same word multiple times: compare “captain”, “chief”, “chef” which captures its evolution.
To understand vowel use in english, just consult the following podcast episodes from The History of English
https://historyofenglishpodcast.com/2020/09/24/episode-141-the-great-vowel-shift-part-1/
https://historyofenglishpodcast.com/2020/10/22/episode-142-the-great-vowel-shift-part-2/
https://historyofenglishpodcast.com/2020/11/24/episode-143-the-great-vowel-shift-part-3/
https://historyofenglishpodcast.com/2020/12/17/bonus-episode-chaucers-purse-and-the-great-vowel-shift/
It’s not necessary to listen to the earlier 140 episodes, but it is helpful.
Damn, I love that podcast.
Yes, I actually just listened to an episode of the wonderful History of English podcast that discussed some of this. I believe the other example given was castle/chateau. It had the “hard c” in Norman French, which came into English after 1066 and the “sh” sound in Old French (around Paris) which came into English much later.
Also related to “captain/chief/chef” is “chapel” - related to a head covering of a particular saint I believe.
Oh, and now I see Qadgop beat me to the podcast recommendation!
are you trying to be funny?
Not just trying - it was funny! 
Me too
I have pointed out elsewhere that there are two words spelled unionized, one with the y sound and one without. They are also hyphenated differently: union-ized, un-ion-ized.
Also lots of these words are pronounced differently in different dialects. My MIL who grew up in Loiusville, said tyube where I say toob. She also said nyooz where I say nooz (for news).
I say choob. Also due sounds like Jew.
And presumably she replied, “No, I don’t share your surname. Why do you ask?”