Installation systems are offered by some ISO images.
If a software upgrade was chosen, the existing package repositories can
eventually be detected from the selected root file system.
A (graphical) user interface is provided so far where the activation can be
toggled for these repositories.
It can happen that the repository configuration was mostly working before.
Thus I would find it occasionally more helpful to reactivate such a
configuration (instead of replacing it with an adjusted variant) for the next
software upgrade attempt.

How will the chances evolve to support such an installation system
configuration option?