Hi @Sisay_Webshet 
. Since this is your first time posting it'd be cool if you also posted something in the forum's Introduce Yourself thread.
ODK Collect is an Android app and so can't be installed on Ubuntu (unless you're using an Android emulator). The Play Store lets users on Android phones install apps so that's why you're seeing that error message. If you'd like to try Collect out try installing it on Android device if you have one. I'd also recommend looking at the docs here.