@Sherlockholmes007 this is still to be solved.
I get the same issue after upgrading to Debian 13 and modernizing sources for repositories.

So now you have 2 types of Debian: the modernized one (with .sources file) and the old style (with .list file).

I think that it is not so difficult checking a condition to act as it corresponds: adding or not the .list or the .sources file.

Thanks,
Joep.