Hmm I would say a plank and side dips and lay with you Bach on the floor and and elevate your head with your arms and then put your knees into fetal position and then put them into like a 90° angle and then all the way out and hold it and then repeat I would say that doesn't tend to hurt my back but it's a hard workout to explain haha. I would also say you can just adjust other workouts to how your back feels because if you can feel your core really burning and feeling like you're working out then you're probably working off those calories and working out your abb so just look for modifications that work for you.
Actually, erlier, i used to workout a lot, a chose one of the 30min video in youtube for core, legs or arms. I have been doing like that for months, everyday. It wasn't bad, but it was hard, now i have some muscle and feel myself great. I don't workout like this anymore, but everyday i do yoga flows and sometimes even yoga for core.
I used to go to the gym and the core exercises were great for building muscles and helping me with my backache. Now due to covid I just walk from work to home and that's the only workout I found safe enough to do. Though I'm trying to find a safe routine to catch up. Maybe tennis in future weeks, it works on the entire body.
Ok so I get up make my bed and it helps me feel organized then I drink a glass of water and that makes me feel refreshed and energized.
I would the wiflde grip pulldown bars at the gym. One interesting video I saw had a girl using a 1.5 liter bottle to rest her upper back on and arch the lower body as a way of helping her posture