Basically if you tried Everything above and still you have the same error "Because i am facing this issue before too" then check which .jar or .aar or module you added may be the one library using ndk , and that one is not supporting 8.0 (Oreo)+ , likewise i am using Microsoft SignalR socket Library adding its .jar files and latterly i found out app not installing in Oreo then afterwards i remove that library because currently there is no solution on its git page and i go for another one.
So please check the library you are using and search about it if you eagerly needed that one.