Similar to what @iestynapmwg said, while upgrading from Ubuntu 20.10 to 21.04 experiencing this slowness on step "searching for obsolete software". Mine took 36 minutes (in my Dell XPS 15 9550 that's not so old).
2021-05-14 08:17:28,617 DEBUG Start checking for obsolete pkgs 2021-05-14 08:41:34,610 DEBUG Finish checking for obsolete pkgs Main difference is that my main culprit seems always package 'libqt5gui5' 2021-05-14 08:37:08,688 DEBUG 'libparams-validationcompiler-perl' scheduled for remove but not safe to remove, skipping 2021-05-14 08:37:08,776 DEBUG package 'libqt5concurrent5' produces an unwanted removal 'libqt5gui5', skipping and lsof command returned "hirsute" sudo lsof /var/lib/dpkg/lock lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/1002/gvfs Output information may be incomplete. lsof: WARNING: can't stat() fuse.portal file system /run/user/1002/doc Output information may be incomplete. COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME hirsute 15215 root 16uW REG 259,5 0 1966936 /var/lib/dpkg/lock -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1874272 Title: Stage "searching for obsolete software" takes a very long time (30 minutes) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1874272/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs