WaterRower are a nice alternative. Not as ‘proper’ as the concept 2 but just as good for the actions and durability.
It’s far more aesthetically pleasing to have in your home, and whilst rowing is far more pleasant to be on. Concepts give a horrible whooshing noise, which if you’re on for any length of time is tedious. A WaterRower sounds far nicer, you can watch the water swash around, and it’s loads quieter.
A friend wrote some rowing training software to compliment the system that comes with it, both RowYo as a cadence trainer for all rowing ergo’s (concepts included), and RowH2O specifically for the WaterRower.