Wilder defined RSI as 100 - 100/(1+RS) where RS = avg. of N days' up closes / avg. of N days' down closes.
The RelativeStrengthIndex implementation at https://github.com/QuantConnect/Lean/blob/master/Indicators/RelativeStrengthIndex.cs#L77 seems to provide via public getters, an AverageGain and AverageLoss, but no "IndexValue". The index is actually correctly calculated but is inside the protected function computeNextValue that I cannot access from my code.

Do I have to manually do this?
RSI(computed) = 100 - 100 / (1 + rsi.AverageGain.Value/rsi.AverageLoss.Value)