could you please add something, that portage (emerge) shows all installed packages, which are obsolete (there's no more ebuild in portage or portage_overlay) should be somthing like 'apt-get autoremove' from debian Reproducible: Always Steps to Reproduce:
In portage-2.2 we have the @unavailable set which seems to match.
This request is resolved by the @unavailable set which is available for a long time.