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On linux it is only 1.3 GB currently (everything: app to run and all its data), because it doesn't have the full NN (NeuralNetwork) as in Windows.
The 6 GB is for Windows, and it may increase from time to time, which requires you to re-sync the NeuralNetwork in such cases

Yes, I run a Bitcoin node too. Checked the folder now, 116 GB.

Ethereum is 110GB from scratch...

what is it now in 2019 ?