Hello!
When building a project using gradle-4.4.1 in the folders ... \ build \ outputs \ apk \ debug and ... \ build \ outputs \ apk \ release files are created ... debug.apk and ... release-unsigned .apk. For some reason, the file ... release-unsigned.apk cannot be installed on the phone (with ... debug.apk there are no such problems).
The parameters of the project being created (figure below).
What am I doing wrong? Maybe you need some additional project settings?