I doing a c++ qt5 commercial app for publishing in ubuntu app store, I installed ubuntu sdk to develop and publish it. My surprise was there is no button for publish it in ubuntu sdk, so I'm ask how to put my app in ubuntu app store ?
Check this link. Its the official Ubuntu web page for developers.
They want you to submit it in a tarball. That way a reviewer can check the source code to make sure it compiles correctly into binary. I believe they also do minor checks for grammar and profanity.