
Niovi D. answered 03/17/20
Native Greek Speaker who grew up bilingual, lived 10+ years in Greece
So, the steadfast rule you described that γ is usually pronounced as the "yuh" stands. Generally a "g" sound (like giraffe) is uncommon in Greek at the beginnings of words (and more common with loanwords, πχ: Γκερνίκα=Guernica).
The "g" sound is written as "γγ" (πχ: αγγελία) or "γκ" (πχ: εγκαίνια). As such, if you're hearing people pronounce what is written as a simple "γ" as "gh", that's usually someone who isn't as comfortable pronouncing γ in the standard fashion, or just an individual idiosyncrasy.