So I'm trying to upgrade from Debian Jessie to Stretch and following the official guide from the wiki.
I came across this section
The upgrade process described in this chapter has been designed for upgrades from “pure” jessie systems without third-party packages. For the greatest reliability of the upgrade process, you may wish to remove third-party packages from your system before you begin upgrading.
$ apt-forktracer | sort reveals I have quite a number of packages from third party sources as well as packages from Jessie-Backport. Most appear to be harmless applications that aren't system dependent but there's also some Java RE in there. I've checked and these packages are supported in Stretch.
Can I safely ignore these third party packages for the upgrade ?