A package is marked for autoremoval if it was installed automatically as a dependency of another package, but currently nothing depends on the automatically installed package anymore.
To give you an example.
In Ubuntu 18.04,
gtkorphan depends on
deborphan so if you install
gtkorphan then
deborphan will be pulled from repository and installed automatically.
Ubuntu 20.04 doesn't provide
gtkorphan anymore. If nothing else depended on
deborphan then it would be marked for autoremoval.
This doesn't mean
deborphan is incompatible. In fact, it was upgraded from 1.7.28.8ubuntu2 to 1.7.32 during the release upgrade. If you want to prevent it from being autoremoved, clear the autoremove flag:
Code:
sudo apt-mark manual deborphan