I now think the proposed gnome-shell version 3.30.1-2ubuntu1.18.10.1 is fine. It doesn't need fixing in itself but it does hit a mutter bug which needs fixing per the above link.
Since they would be released at different times anyway, and the secondary regression is probably already visible in disco, we may as well release the gnome-shell fix to cosmic now. The mutter fix is complete and will come soon (only waiting on upstream review).
I now think the proposed gnome-shell version 3.30.1- 2ubuntu1. 18.10.1 is fine. It doesn't need fixing in itself but it does hit a mutter bug which needs fixing per the above link.
Since they would be released at different times anyway, and the secondary regression is probably already visible in disco, we may as well release the gnome-shell fix to cosmic now. The mutter fix is complete and will come soon (only waiting on upstream review).