This is super touchy, and here is what I did to make it happy and stable.
This does not address if UEFI decides to write to one of these mirrors. Someone else has a systemd unit to assemble with resync.
In the past, I used someone else’s bypass script, but this was cleaner, and works in 18 and 20 LTS.
### Filesystem / Mirror for EFI / UEFI booting:
mdadm raid 1, metadata 1.0
vfat filesystem for /boot/EFI
### Proper GRUB package
apt-get purge grub\*
apt-get install grub-efi
apt-get autoremove
### Settings that seem to not stick
dpkg-reconfigure -p low grub-efi-amd64
Update NVRAM variables to automatically boot into Debian? NO
echo "grub-pc grub2/update_nvram boolean false" | debconf-set-selections
echo "grub-pc grub-efi/install_devices multiselect /dev/md0" | debconf-set-selections
### Grub config
update-grub
grub-install --no-nvram /dev/md0
### UEFI boot list (variables)
[root@tsm2: /root]
/bin/bash# efibootmgr -?
efibootmgr: invalid option -- '?'
efibootmgr version 17
usage: efibootmgr [options]
-a | --active sets bootnum active
-A | --inactive sets bootnum inactive
-b | --bootnum XXXX modify BootXXXX (hex)
-B | --delete-bootnum delete bootnum
-c | --create create new variable bootnum and add to bootorder
-C | --create-only create new variable bootnum and do not add to bootorder
-D | --remove-dups remove duplicate values from BootOrder
-d | --disk disk (defaults to /dev/sda) containing loader
-r | --driver Operate on Driver variables, not Boot Variables.
-e | --edd [1|3|-1] force EDD 1.0 or 3.0 creation variables, or guess
-E | --device num EDD 1.0 device number (defaults to 0x80)
-g | --gpt force disk with invalid PMBR to be treated as GPT
-i | --iface name create a netboot entry for the named interface
-l | --loader name (defaults to "\EFI\ubuntu\grub.efi")
-L | --label label Boot manager display label (defaults to "Linux")
-m | --mirror-below-4G t|f mirror memory below 4GB
-M | --mirror-above-4G X percentage memory to mirror above 4GB
-n | --bootnext XXXX set BootNext to XXXX (hex)
-N | --delete-bootnext delete BootNext
-o | --bootorder XXXX,YYYY,ZZZZ,... explicitly set BootOrder (hex)
-O | --delete-bootorder delete BootOrder
-p | --part part partition containing loader (defaults to 1 on partitioned devices)
-q | --quiet be quiet
-t | --timeout seconds set boot manager timeout waiting for user input.
-T | --delete-timeout delete Timeout.
-u | --unicode | --UCS-2 handle extra args as UCS-2 (default is ASCII)
-v | --verbose print additional information
-V | --version return version and exit
-w | --write-signature write unique sig to MBR if needed
-y | --sysprep Operate on SysPrep variables, not Boot Variables.
-@ | --append-binary-args file append extra args from file (use "-" for stdin)
-h | --help show help/usage
[root@tsm2: /root]
/bin/bash# efibootmgr -v
BootCurrent: 0019
Timeout: 5 seconds
BootOrder: 0005,0006,0007,000C,0019,0018
Boot0000 Startup Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)....ISPH
Boot0001 System Information FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0002 Bios Setup FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0003 3rd Party Option ROM Management FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0004 System Diagnostics FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0005* nvme0_grub HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\ubuntu\grub.efi)
Boot0006* nvme1_grub HD(1,GPT,aa23256a-95c6-4148-b56c-c8861fc7966a,0x800,0x8e800)/File(\EFI\ubuntu\grub.efi)
Boot0007* nvme2_grub HD(1,GPT,1f7f7f5b-2a89-4d87-a617-6ccaf15078dd,0x800,0x8e800)/File(\EFI\ubuntu\grub.efi)
Boot0008 Boot Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0009* Kingston DataTraveler 3.0 408D5CE57214E331293064F6 BBS(USB,USB1,0x900)/PciRoot(0x0)/Pci(0x1d,0x0)......ISPH
Boot000B Network Boot FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot000C* nvme3_grub HD(1,GPT,cb8bc8b4-affc-4765-97c2-72af0c615d44,0x800,0x8e800)/File(\EFI\ubuntu\grub.efi)
Boot000E* IPV6 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv6([::]:<->[::]:,0,0)N.....YM....R,Y.....ISPH
Boot0010* IBA GE Slot 00C8 v1550 BBS(Network,Network1,0x0)/PciRoot(0x0)/Pci(0x19,0x0)......ISPH
Boot0011 USB: PciRoot(0x0)/Pci(0x1d,0x0)N.....YM....R,Y.....ISPH
Boot0012 HP Recovery FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0013* hp PLDS DVDRW DU8AESH PciRoot(0x0)/Pci(0x1f,0x2)/Sata(0,0,0)N.....YM....R,Y.....ISPH
Boot0014* hp PLDS DVDRW DU8AESH BBS(CDROM,CDROM1,0x400)/PciRoot(0x0)/Pci(0x1f,0x2)......ISPH
Boot0018* ubuntu HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\ubuntu\shimx64.efi)....ISPH
Boot0019* ubuntu HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)....ISPH
Boot001A* IPV4 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv4(0.0.0.00.0.0.0,0,0)N.....YM....R,Y.....ISPH
[root@tsm2: /root]
/bin/bash# efibootmgr -B -b 0005
/bin/bash# efibootmgr -B -b 0006
/bin/bash# efibootmgr -B -b 0007
/bin/bash# efibootmgr -B -b 0009
/bin/bash# efibootmgr -B -b 000c
/bin/bash# efibootmgr -B -b 0018
BootCurrent: 0019
Timeout: 5 seconds
BootOrder: 0019
Boot0000 Startup Menu
Boot0001 System Information
Boot0002 Bios Setup
Boot0003 3rd Party Option ROM Management
Boot0004 System Diagnostics
Boot0008 Boot Menu
Boot000B Network Boot
Boot000E* IPV6 Network - Aquantia AQtion 10Gbit Network Adapter
Boot0010* IBA GE Slot 00C8 v1550
Boot0011 USB:
Boot0012 HP Recovery
Boot0013* hp PLDS DVDRW DU8AESH
Boot0014* hp PLDS DVDRW DU8AESH
Boot0019* ubuntu
Boot001A* IPV4 Network - Aquantia AQtion 10Gbit Network Adapter
[root@tsm2: /root]
/bin/bash# efibootmgr -v
BootCurrent: 0019
Timeout: 5 seconds
BootOrder: 0019
Boot0000 Startup Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)....ISPH
Boot0001 System Information FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0002 Bios Setup FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0003 3rd Party Option ROM Management FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0004 System Diagnostics FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0008 Boot Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot000B Network Boot FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot000E* IPV6 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv6([::]:<->[::]:,0,0)N.....YM....R,Y.....ISPH
Boot0010* IBA GE Slot 00C8 v1550 BBS(Network,Network1,0x0)/PciRoot(0x0)/Pci(0x19,0x0)......ISPH
Boot0011 USB: PciRoot(0x0)/Pci(0x1d,0x0)N.....YM....R,Y.....ISPH
Boot0012 HP Recovery FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0013* hp PLDS DVDRW DU8AESH PciRoot(0x0)/Pci(0x1f,0x2)/Sata(0,0,0)N.....YM....R,Y.....ISPH
Boot0014* hp PLDS DVDRW DU8AESH BBS(CDROM,CDROM1,0x400)/PciRoot(0x0)/Pci(0x1f,0x2)......ISPH
Boot0019* ubuntu HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)....ISPH
Boot001A* IPV4 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv4(0.0.0.00.0.0.0,0,0)N.....YM....R,Y.....ISPH
[root@tsm2: /root]
/bin/bash# efibootmgr -c -d /dev/nvme0n1 -L nvme0_grub -l '\EFI\grub\shimx64.efi'
/bin/bash# efibootmgr -c -d /dev/nvme1n1 -L nvme1_grub -l '\EFI\grub\shimx64.efi'
/bin/bash# efibootmgr -c -d /dev/nvme2n1 -L nvme2_grub -l '\EFI\grub\shimx64.efi'
/bin/bash# efibootmgr -c -d /dev/nvme3n1 -L nvme3_grub -l '\EFI\grub\shimx64.efi'
/bin/bash# efibootmgr -o 0005,0006,0007,0009,00019
BootCurrent: 0019
Timeout: 5 seconds
BootOrder: 0005,0006,0007,0009,0019
Boot0000 Startup Menu
Boot0001 System Information
Boot0002 Bios Setup
Boot0003 3rd Party Option ROM Management
Boot0004 System Diagnostics
Boot0005* nvme0_grub
Boot0006* nvme1_grub
Boot0007* nvme2_grub
Boot0008 Boot Menu
Boot0009* nvme3_grub
Boot000B Network Boot
Boot000E* IPV6 Network - Aquantia AQtion 10Gbit Network Adapter
Boot0010* IBA GE Slot 00C8 v1550
Boot0011 USB:
Boot0012 HP Recovery
Boot0013* hp PLDS DVDRW DU8AESH
Boot0014* hp PLDS DVDRW DU8AESH
Boot0019* ubuntu
Boot001A* IPV4 Network - Aquantia AQtion 10Gbit Network Adapter
[root@tsm2: /root]
/bin/bash# efibootmgr -v
BootCurrent: 0019
Timeout: 5 seconds
BootOrder: 0005,0006,0007,0009,0019
Boot0000 Startup Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)....ISPH
Boot0001 System Information FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0002 Bios Setup FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0003 3rd Party Option ROM Management FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0004 System Diagnostics FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0005* nvme0_grub HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)
Boot0006* nvme1_grub HD(1,GPT,aa23256a-95c6-4148-b56c-c8861fc7966a,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)
Boot0007* nvme2_grub HD(1,GPT,1f7f7f5b-2a89-4d87-a617-6ccaf15078dd,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)
Boot0008 Boot Menu FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0009* nvme3_grub HD(1,GPT,cb8bc8b4-affc-4765-97c2-72af0c615d44,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)
Boot000B Network Boot FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot000E* IPV6 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv6([::]:<->[::]:,0,0)N.....YM....R,Y.....ISPH
Boot0010* IBA GE Slot 00C8 v1550 BBS(Network,Network1,0x0)/PciRoot(0x0)/Pci(0x19,0x0)......ISPH
Boot0011 USB: PciRoot(0x0)/Pci(0x1d,0x0)N.....YM....R,Y.....ISPH
Boot0012 HP Recovery FvVol(cdbb7b35-6833-4ed6-9ab2-57d2acddf6f0)/FvFile(9d8243e8-8381-453d-aceb-c350ee7757ca)......ISPH
Boot0013* hp PLDS DVDRW DU8AESH PciRoot(0x0)/Pci(0x1f,0x2)/Sata(0,0,0)N.....YM....R,Y.....ISPH
Boot0014* hp PLDS DVDRW DU8AESH BBS(CDROM,CDROM1,0x400)/PciRoot(0x0)/Pci(0x1f,0x2)......ISPH
Boot0019* ubuntu HD(1,GPT,e41eb9e0-6606-411a-bb83-bed7577f29b3,0x800,0x8e800)/File(\EFI\grub\shimx64.efi)....ISPH
Boot001A* IPV4 Network - Aquantia AQtion 10Gbit Network Adapter PciRoot(0x0)/Pci(0x1,0x0)/Pci(0x0,0x0)/MAC(88c9b3bfa1e9,0)/IPv4(0.0.0.00.0.0.0,0,0)N.....YM....R,Y.....ISPH
[root@tsm2: /root]
/bin/bash# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.3 LTS
Release: 20.04
Codename: focal
[root@tsm2: /root]
/bin/bash# uname -a
Linux tsm2 5.4.0-97-generic #110-Ubuntu SMP Thu Jan 13 18:22:13 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux