Hello, there are two ways to fix broken back glass on iPhone 8-11 series; replace the glass back panel itself or replace the housing (new metal sides and back glass). Replacing the back glass as a DIY task is really hard and requires lots of patience heat (or extreme cold), and if poorly done then the new glass won’t stick flush. If you are experienced at repairs the easier method would be to replace the housing, by transferring all the internal components of your current 8 Plus into the new housing. If you are newer to repair, but are confident and are willing to take the risk you can pay a bit more and get a housing that has the small parts (dock connector, flex cables, QI coil etc.) already installed. [br]
Another good new option is paying a repair place who has professional equipment. The use lasers to get rid of the glue and it will almost always look better than if it is manually done. REWA has a demo on YouTube. This will cost more than the other options, but still be cheaper than Apple.
Otherwise a case or a skin would also be a easy way to hid the cracks (: