I too have benefited recently (since 3 months) from rowing, and started by simply emulating Dark Horse rowing on a laptop set to the front/side of the machine. I really like Rowalong channel now, because he gives effort instructions in terms of your best 2k pace. For example, he'll say "2k+18" for the next interval so if your best 2k time had average 2:00/500m pace, then row currently at 2:18 pace. Compare to Dark Horse who might say "Go at 75% effort" which suffers from subjective self reporting.

If you haven't seen it, https://rowinglevel.com has tables for various distances and ages. It intimidated me at first (these times are fast!) but reaching beginner and novice when they once felt completely impossible is a good feeling.

> It took months to get up to speed with a lot of initial back pain, but the strength gained has done away with back issues I used to have.

This has been my biggest benefit as well.