Hello everyone. I saw recently a comment about an app for macOS that allows you to use CompetitiveCompanion in Safari (Big Sur); it's basically a translation of the original extension. It's called Codeforces Web Tool. It also has the Codeforces Rating Prediction feature. Since I didn't know about it until some months/weeks ago, this could have happened to other folks too.
This is the app.
You could also use Userscripts and use the CF Predictor script with it.
Indeed. But for the parser feature you can’t use user scripts.