[PureOS] PureOS | Debian delta

Hi,

What is the PureOS < > Debian delta? I assume that it is a set of patches that we apply to packages, like the work Jonas does on Firefox ESR, as well as the fact that we do not have a non-free repo.

Knowing the delta would help us to understand how to move the work being done on the L5 phone into our CD system for example. Just documenting it would be a big help.

Where can I find this information?

Cheers,

Jeremiah