@klara I pronounce it KOO-beh-leh, the vowel in the first syllable kind of like a short german ü
the Romans often called Her "Magna Mater" (Great Mother), not sure how they would have pronounced "Cybele" but maybe like "KOO-beh-leh" or "KEE-beh-leh", with the OO like the normal latin "u". Apparently Y is sometimes an EE and sometimes OO