Thank you for taking the time to report this issue and helping to make Ubuntu better.
In the 'dpkg-terminal-log' output I notice grub-install: error: cannot open `/boot/efi/EFI/ubuntu/grubx64.efi': Read-only file system. In your 'dmesg' output are many errors on a FS that caused the RO trip, ie. [ 93.081833] FAT-fs (sda2): error, corrupted directory (invalid entries) [ 93.081837] FAT-fs (sda2): Filesystem has been set read-only [ 93.082972] FAT-fs (sda2): error, corrupted directory (invalid entries) [ 93.087589] FAT-fs (sda2): error, corrupted directory (invalid entries) [ 93.095266] FAT-fs (sda2): error, corrupted directory (invalid entries) [ 4309.733625] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.733654] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.734815] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.734832] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.739088] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.739111] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.746569] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) [ 4309.746601] FAT-fs (sda2): error, fat_get_cluster: invalid cluster chain (i_pos 0) I suspect your issue isn't bug related, but you've an EFI partition that likely needs a `fsck` to correct file system errors, thus support would be more appropriate, eg. https://answers.launchpad.net/ubuntu . You can also find help with your problem in the support forum of your local Ubuntu community http://loco.ubuntu.com/ or asking at https://askubuntu.com or https://ubuntuforums.org , or for more support options please look at https://discourse.ubuntu.com/t/community- support/709 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1868198 Title: package grub-efi-amd64-signed 1.128.2+2.04-1ubuntu12.2 failed to install/upgrade: installed grub-efi-amd64-signed package post- installation script subprocess returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2-signed/+bug/1868198/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs