It looks like the upgrade failure is ultimately caused by pacakges from the ondrej/php PPA. In particular, libgd3 2.3.0-2+ubuntu16.04.1+deb.sury.org+1 depends on a version of libpng12-0 that creates a conflict for usrmerge.
Please try removing packages from ondrej/php using the `ppa-purge` tool, and then try the upgrade again. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1976195 Title: Upgrade abort from ubuntu 20.04 to ubuntu 21.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1976195/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs