How to pronounce 翁 in Mainland China and Taiwan?
This concerns a mid-back vowel pair of [ɤ]/[o] (in IPA symbol), where [ɤ] is unrounded and [o] rounded. In today's mandarin in China, it's unrounded; in taiwan, it is sometimes rounded and sometimes unrounded, depending on the preceding consonant. If the preceding consonant is labial then pinyin o is the rounded [o], otherwise the unrounded [ɤ]. The Taiwanese pronunciation was also the older mandarin pronunciation and can still be heard in many regions' accents in China, but not in today's standard mandarin any more.