Hi
I have one from Waterrower Ive only rented it for now. But unfortunately it is anything but cheap, unless you get a rental device that is already several years old (but overhauled)...
The device has the advantage that it takes up little space, because you can put it upright after use and roll it into a corner room. To learn the technique, there are some good videos, also on the homepage of the company are some tips for complementary strengthening exercises... If you enjoy playing games, you can also connect the device to the internet and virtually row against other people - I have not tried it yet, but I will because I also enjoy the rowing a lot.
You can find here some good models:
https://home2outdoor.com/best-rowing-machine/. When I looked around for some, the site was my starting point.