PBK Reviews did a nice disassembly video of the Nokia XR21 after doing a drop test of the device. The disassembly seems quite simple although you’ll need a heat gun to loose the adhesive of the back cover.
A few things can be seen which are characteristic of this device, the huge strip of adhesive that keeps the back cover, a ton of screws that keep the internals tightly fixed, and a new colour of the motherboards which are now black.
Another thing I noticed is that there was a place for a wireless charging coil on the inside of the device, but that somehow couldn’t be inserted. Actually, when tapping the back, I can sense the hollowness of the body which is something you don’t get with XR20. The battery on XR21 has pull tabs which suggest once you got inside of the device, you can easily remove the old battery and place a new one.
PBK gave XR21 a 6.5 out of 10 for repairability which is basically a good score for a tightly packed device designed to withstand the drops and various other kicks.