When people see the word “Ubuntu“, they either try and figure out how it is pronounced in African, or try to impose their own pronunciation on it. I’ve seen in blogs people say everyone they knows calls it “You-bun-too” – to which I would ask should “umbrella” be pronounced “yoom-brel-la“? While English can be weird in the least when it comes to vowels repeated in words sounding different, most nationalities – be they European or African – have a single sound per vowel.
The u in “Ubuntu” is the same no matter what part of the word it is in, so the word is pronounced “oo-boon-too“. Similarly, “Kubuntu” is “koo-boon-too“, and “Xubuntu” is “zoo-boon-too” (and not “ex-oo-boon-too” as I have heard it referred to).