Mispronunciation of "entrepreneur"

That’s just a regular pronunciation of the spelling “-neur” in English. The word “amateur” also has variant pronunciations with the vowel of “cure”/“manure”. (By that I mean an r-controlled “long u” sound, where the influence of the following r has caused the vowel to sound like the lax “oo” of “book” for some speakers. Other speakers have merged the “cure” vowel into either the “nurse” vowel or the “north”/“force” vowel.)

French doesn’t actually have exactly the same vowel here as in English “purr”. It’s close or approximately equivalent, but neither English pronunciation is actually “correct” if your standard is native French speakers’ pronunciation.

If that isn’t your standard, I think it’s somewhat arbitrary to prefer one anglicized pronunciation over another.