Currently on a Samsung note 8, and aside from wear and tear, I’m pretty happy with it. I’ve replaced the battery, the camera glass, the rear glass, it has a bit of burn in on the screen, and is beginning to have some issues with the power button registering double clicks instead of only one. Actually pretty easy to work on if you have messed with electronics before, mix of glue and screws to disassemble.
My next logical phone would be a Sony Xperia 1 mark vi, but that isn’t really available for the US (I’m on AT&T, and they have a white list), so I’m just staying with my Samsung for now as there aren’t really any flagships with headphone jacks, expandable storage, and decent repairability.
I know this is a weird answer, but try sleeping in a good drawn end hammock (think an Eno hammock, but try to find one that is longer). If you sleep diagonally, it cradles your body amazingly. I’ve been sleeping in one for a couple of years, and it’s both gotten rid of my tossing/turning and helped pretty drastically with my back.