We had a look through the apparmor denials and none looked related. The fishy error is:
cp: cannot stat '/snap/opera-developer/78/gnome-platform/usr/share/mime': No such file or directory
Because the directory does exist, my suspicion was lack of user permissions to it.
The real path (bind mounted within your snap) being: /snap/gnome-3-28-1804/current/usr/share/mime