Samsung's Galaxy S21 Ultra earns a 3 out of 10 on our repairability scale (10 is easiest to repair):

All the important fasteners are identical Phillips screws in size and length, simplifying the repair process.

Many components are modular and independently replaceable, but the missing modular display cable and polycarbonate rear panel from the regular S21 are a step backward.

The rear panel is glued down and difficult to remove, even more so thanks to the new ridge around the camera bump's edge.

The battery and display continue to be difficult repairs, as both components are held down with some serious adhesive and require a fair bit of disassembly to get to.