Comment 10 for bug 2018037

Not sure how "works for me on 22.04" is taken to be a solution for a problem reported on 23.04.

I've just looked on 2 of my systems (both 23.10).

The one which has been upgraded from 22.04 is OK.

The one which was a fresh install (new system) of 23.10 is not. In fact it doesn't show any sources at all.

That issue seem to be related to have *.sources files in sources.list.d/ (which works fine with apt, and is how launchpad now sets things up for, e.g., grub-customizer *and* backports).
These entries do not show up in Settings. And it seems that if you have enough of them (I had 5 of them) the entire Default Source section is missing from Settings (and, oddly, the Firmware Updates, Snap and Flatpak section then show in the reverse order).

So, it looks as though the Software Sources issue is now OK, but there are other issues.

I'll open a new bug report for that.