Clean Debian testing (amd64) system installed in a vm using latest iso. When opening GNOME Software, switching to the "Updates" tab and clicking the spinner button in header to check for new updates, the check immediately finishes (after a second or two) and does not seem to actually fetch any new update info. I am including a verbose gnome-software log from after clicking the button.
This part of the log may be related:
app invalid as no summary system/package/*/debian.www.debian-12/*
P.S. I have noticed the cdrom error in the log, however it looks like that disabling the cdrom source in /etc/apt/sources.list did not help.