Fight Scores (similar, but not the same) is a good app. Allows you to score, put official results, and notes for the fight. There were over 400 people scoring the Usyk fight live when I was watching/scoring it.
I'm pretty sure you can do it on Boxrec. Just gotta click on the score button for that particular fight. I just use an offline one that I found on the app store.
Boxing News app I think lets you score fights and do predictions