Just like the title says, Is it safe to update your semi-unlocked IPhone to IOS12.1? the answer is YES and MAYBE.
Many are hesitant at first because they may loose the semi unlocked feature of their IPhones. Some brave IPhone 6 users took the risk and update their phones with crossed fingers, and YES for the reason of a successful update and fortunately no one has ever felt sorry for what they've did on the other-hand MAYBE because most of the respondents are IPhone 6 users, and not quite sure if this is applicable for other IPhone units that are semi unlocked.
So update at your own risk, if you were really eager to experience the new IOS 12.1 then do so, but if there's no issues on your phone leave it as is.
Comment down below if you are one of the other IPhone user who had successfully updated their phone to IOS 12.1.
Here are the features of the IOS12: https://www.apple.com/ph/ios/ios-12/