Grub on RAID1, keep from failing on next update?

I have /boot/ on /dev/md0, with two partitions:

• /dev/sda1
• /dev/sdb1

I had a problem when running apt upgrade because I had to replace sdb and the new drive wasn't in the grub config. I got things working with a grub-install, but my problem is I don't have the right devices in the grub config for the next update. For instance:

~# debconf-show grub-common
  grub-efi/install_devices_empty: false
  grub-efi/install_devices_failed: false
* grub-efi/install_devices_disks_changed: /dev/disk/by-id/ata-WD_easystore_240GB_<redacted>-part1
  grub-efi/partition_description:
* grub-efi/install_devices: /dev/disk/by-id/ata-WD_easystore_240GB_<redacted>-part1

In the above, you can see grub is installing on sda1. This used to have sdb1 as well, but now it doesn't. So if sda fails, no booting for me.

I've read online that running dpkg-reconfigure grub-pc can solve this, but that doesn't work for me:

~# dpkg-reconfigure grub-pc
dpkg-query: package 'grub-pc' is not installed and no information is available
Use dpkg --info (= dpkg-deb --info) to examine archive files.
/usr/sbin/dpkg-reconfigure: grub-pc is not installed
~# apt list --installed |grep grub

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

grub-common/focal-updates,now 2.04-1ubuntu26.13 amd64 [installed,automatic]
grub-efi-amd64-bin/focal-updates,focal-security,now 2.04-1ubuntu44.2 amd64 [installed,automatic]
grub-efi-amd64-signed/focal-updates,focal-security,now 1.167.2+2.04-1ubuntu44.2 amd64 [installed]
grub-efi-amd64/focal-updates,focal-security,now 2.04-1ubuntu44.2 amd64 [installed]
grub2-common/focal-updates,now 2.04-1ubuntu26.13 amd64 [installed,automatic]

Any ideas on how I fix this for future updates?