The webUI won't calculate anything for you, so if you want to see accuracy, precision etc. you'll have to calculate those in your code and then report them as scalers for the UI to know what they are.

As you said, sklearn models don't work with iterations, so when using the logger to report the scalar, you can just set the iteration nr to 0.
The downside of that is that your scalars will still be plotted, only as a single point in the graph instead of in a table. This is a known open issue for now ( https://github.com/allegroai/clearml/issues/400 ), but would be cool if you could build it and contribute it yourself if you can 😄