Press E at the GRUB menu. Find the line saying save_env recordfail and delete all «- this was not needed

Only these steps:

sudo -i

Then, run each command, one-by-one.

cd /boot/grub
rm grubenv
grub-editenv grubenv create
grub-editenv grubenv set default=0
grub-editenv grubenv list
update-grub

Nor anything after these commands. Simply reboot and it should be fixed.

• Ubuntu 20.04.2 LTS

• Grub errors
• Reinstall grub on mdraid1 array

• https://askubuntu.com/questions/191852/error-invalid-environment-block-press-any-key-to-continue/191865#191865