"structured APT" was added as an optional feature with https://projects.theforeman.org/issues/35959

See the documentation for enabling structured APT in the current release: https://docs.theforeman.org/3.16/Managing_Content/index-katello.html#Structured-apt-content

We now plan to make the feature mandatory with the Katello release that this ticket ends up in.

As part of the upgrade to that Katello version, any non-structured deb type content must automatically be migrated to structured.

The setting to enable/disable structured APT will be dropped, and all code will be amended to reflect this new reality.

With this change, all deb type content past the relevant Katello upgrade will be assumed to be structured APT content, and there will be no non-structured deb type content.

Note: There will still remain a fallback mechanism for very old Pulp repo versions, that were created in a way where structure content is missing on the Pulp side. This is unavoidable because the structure information for such Pulp repo versions is lost.