Did you set grub-pc/install-devices (e.g. through package configuration) yourself, or is it from the installer?
> * grub-pc/install_devices: /dev/disk/by-id/md-name-ubuntu-server:0
I'd expect grub-pc/install_devices to contain the raw disks themselves e.g. to be /dev/vda /dev/vdb and not the raid.
Did you set grub-pc/ install- devices (e.g. through package configuration) yourself, or is it from the installer?
> * grub-pc/ install_ devices: /dev/disk/ by-id/md- name-ubuntu- server: 0
I'd expect grub-pc/ install_ devices to contain the raw disks themselves e.g. to be /dev/vda /dev/vdb and not the raid.