Forward lean comes from the hips, not back. Bending over at the lower back is unsafe - don't do it. Rock your hips.
When you lean forward you should feel your butt rock on the seat. If you don't then you're bending your lower back into a weak position, which is *not* the goal of forward lean - lower back bend only creates back problems. If you don't feel the rocking try sitting near the front edge of the erg seat, that may help you feel it.
Sitting right now in your chair reading this, bend your head down without moving your hips/butt. Your lower back bends. Now sit up and do this again while keeping your back straight. You should feel your butt rock forward on the chain cushion and your weight shift from the buttock more forward and your upper legs/hamstrings press against the seat cushion. This is the motion.
There are some videos on "grabbing your cheeks" that try to explain the feel of the hips/pelvis rolling forward. By pulling the cheeks up on forward lean you force the pelvis forward where it should be.
You can also look at squat videos. If you do squats there's a point where your butt goes from underneath you to poking out. That motion where the pelvis rotates and the butt pokes out is the forward lean motion. Look also at people doing squats badly wrong -- their butt stays under their chest and they curve their lower back when they learn over to get the weight -- don't do that rowing or weight lifting.
Checkout this video on Connor McGregor rowing. I couldn't watch more than a few minutes. You can see the lack of hip motion and large lower back bend among other things.
https://youtu.be/gmKkWYGN1yE?t=95 Video could be clearer on how to fix it, but you can see the problem clearly.
If you can create video for Rowerup you can also use technology to help you. Put a letter size piece of paper with a V behind you. V is 22 degrees forward, 22 back. (protractor or you can split a 90 degree angle in half twice). Compare your back angle - it should match. Video is a great way to do this. If you can use a monitor and compare your back to the V while rowing its even better. Put the V picture where the camera can see it behind you at the catch and in front of you at the finish. IT's easy to compare the angles. Do fix any lower back bend and get your hip swing right before fine tuning the angle -- the correct angle done by curving your lower back is really bad.
Too much lean back builds great abs, but doesn't create rowing power and uses energy you could use rowing. But it does make abs, and is safe. Your choice there. Getting rid of some back lean when your core gets tired, returning to the 22 degree lean back, is a good thing if you are using a larger lean back.