sorry I've decided the not-returning to prompt is normal behavior.
I enabled -proposed on x86_64 box, upgraded and had same behavior using 3.30.2-0ubuntu7
I booted another partition [x86[ install on this dx6120 (different QA test), update & upgraded software and it has "Installed: 3.30.2-0ubuntu5" for gnome-software - got identical behavior.
I ran it on my normal workstation (ver 0ubuntu5) & it returned to $prompt almost immediately; before I had a chance to do anything with gnome-software - very different behavior.
sorry I've decided the not-returning to prompt is normal behavior.
I enabled -proposed on x86_64 box, upgraded and had same behavior using 3.30.2-0ubuntu7
I booted another partition [x86[ install on this dx6120 (different QA test), update & upgraded software and it has "Installed: 3.30.2-0ubuntu5" for gnome-software - got identical behavior.
I ran it on my normal workstation (ver 0ubuntu5) & it returned to $prompt almost immediately; before I had a chance to do anything with gnome-software - very different behavior.
So please ignore my return-to-prompt comments..