Now that the final version of Ubuntu 20.04 LTS is available could you try installing with it? Additionally the crash was due to a failure resolving the IP addresses for the Ubuntu archive.
** Changed in: grub-installer (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1873581 Title: install from 19.10 --> 20.04 crashed system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1873581/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs