This, too. The point is that "Uber" by virtue of being a proper name in English is entirely unrelated to the German word "über", even if that may be where its etymological roots lie. This is a perfectly natural process.

I mean, you wouldn't catch anyone on German television pronounce Zuckerberg's name as /ʦʊkɐbɛɐk/, even if it may be of German (Jewish, I presume?) origin.

PS: I think the Duden and Wiktionary are full of shit -- I've never heard anyone in Germany pronounce "Berg" with an actual "r". Maybe I'm missing some subtleties of German phonetic transcription here, but that's an /ɛɐ/ diphthong if I've ever seen one.