how to create an EFI boot partition

https://askubuntu.com/questions/743095/how-to-prepare-a-disk-on-an-efi-based-pc-for-ubuntu

Using GParted, we can

• create a fat32 1st primary partition of size 128 MB or 256 MB or something like that (needs to be first or at least within the first 2.2 TB only if the disk is > 2.2 TB)
• after creating the partition, add the flags boot and esp

Then this partition will be recognized as an EFI /boot partition by Linux installers as well as Windows. For Windows10/11 there is the additional requirement to make "C drive" GPT partitioned instead of MBR partitioned. With GParted, this is via the new partition table - GPT option,

https://www.diskpart.com/gpt-mbr/gparted-create-gpt-partition-7201.html

And to mount the EFI partition if it exists, from a live CD or USB,

https://askubuntu.com/questions/926398/how-to-mount-the-efi-system-partition-using-ubuntu-16-04-live-cd

sudo fdisk -l

will list the EFI partition as "type" "EFI System", and then we can mount the identified partition as

sudo mount /dev/sda1 /mnt

or whatever.