sudo apt install --reinstall libsigc++-2.0-0v5 this fixed it. Not a problem with aptitude. It seems I have a couple of problems with installed library packages after a fresh install.
** Changed in: aptitude (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1851925 Title: Fresh install of aptitude is broken - missing dependency? To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/aptitude/+bug/1851925/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs