Uber isn't a German word. It's (originally) a colloquial word in some (American) English sociolects. It's based on German "über" and started as a loanword, but like many such words it has taken on an entirely unrelated meaning of its own.
I'm pretty sure I've seen "uber" (with either spelling but pronounced in English) on the web and on IRC as early as the 1990s. It likely spread beyond the online use when the web became mainstream.
Disclaimer: German native speaker who used to spend way too much time around linguists.
Yeah, Wiktionary calls the English loanword (without umlaut) /ˈuːbər/ and the German /ˈyːbɐ/. I think it's been a fairly ironic productive prefix in some people's informal English for a while, often hyphenated, like "uber-cool", "uber-interesting", ?"uber-dangerous". (Latin "super" is cognate with German über as well as Greek "ὑπέρ" (hyper)!)
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.
I'm pretty sure I've seen "uber" (with either spelling but pronounced in English) on the web and on IRC as early as the 1990s. It likely spread beyond the online use when the web became mainstream.
Disclaimer: German native speaker who used to spend way too much time around linguists.