Yoo-fi? Yoo-ef-ee?
They shoulda made it easier to pronounce if they wanted people to call it that
What does lowercase have to do with anything?
The only thing that differentiates an acronym from an initialism is if it’s easily pronounceable as a word.
GUI is. GIF is. PDF is not. NASA is, NSA is not. SCUBA is. LASER is. FBI, ATM, URL, FYI are not.
That’s really it. UEFI doesn’t have a real direct pronunciation to it. So it’s just U-E-F-I.