I just bought myself a Concept 2 Rower. I used one at Crossfit a couple of times.
I bought it with a Polar H7 Heart Rate strap.
This allows rowing with heart rate monitoring.
I will be using the same MAF heart rate number of 180 minus age (range of plus 0 minus 10). For me, at 58 years of age, that’s 112 – 122 bpm.