Do you sleep on your back? On side?
I cannot sleep on any mattress on my back anymore. I get lower back pain on a tempur-pedic foam, a regular soft top mattress or firm, and I tried laying down for a bit on my son’s sleepnumber but got up aching. When I’m on my back my knees bend backwards - a new problem when menopause took away my estrogen and skin/tendon elasticity. A pillow under my knees or a mattress that lifts my knees work, but neither keep my back from hurting.

I can sleep on my side, with extra pillows for positioning on just about any mattress except those that sag too much in the middle.
I loved our tempur-pedic but my husband got tired of it so we replaced it with a spring mattress with a soft top. Works okay.

I guess you’ve tried side sleeping with a pillow between your knees? Some of the commercial strap-on foam cushions made for this purpose are not made correctly. They don’t separate the knees enough. The separation keeps the back from twisting which is what so many people find painful in the morning.
I also do better if I tuck a pillow under my arm, the one on the high side. But it’s too much trouble to cope with two pillows when I want to turn over, which I do multiple times during the night. I think a long body pillow might work - but it keeps me too separate from my husband - neither of us like that.

Side sleepers - do you have a mattress you like? How about a pillow? I haven’t found a pillow I like much for side sleeping - I’ve tried a bunch.