partitioning – Does UEFI must have en EFI partition to boot?

I’m very confused about the UEFI terminology. I have read many pages and this is what I know: (please correct me if I’m wrong)

UEFI can boot from SATA and NVMe disks
UEFI can boot from MBR and GPT disks
EFI partitions are just FAT32 partitions labeled EF00 or such code. Unclear about this
UEFI boot does not read the MBR and looks for “boot entries” that must be manually (or installed by the OS) configured

The last point leads to my question
What I don’t know and it is my main doubt: does UEFI MUST have a EFI partition to boot?

On the same context: how does this EFI partition (AKA ESP) relates to the so called secure boot? What exactly secure boot means?

A little background: I have a dual boot laptop with 1 TB NVMe disk. It has four MBR partitions and I want to convert it to GPT:

Ubuntu 22 bootable
Empty. It was a swap partition that Ubuntu no
longer uses. This one I want to use as ESP in case is a must
Windows 10 NTFS main bootable partition
Windows NTFS second hard disk

This layout may seem odd. The reason is time. I installed and formatted a laptop long time ago, during the preUEFI/preSSD eras. I’ve used Clonezilla over time to copy the disk to new laptops. Although it boots fine both Ubuntu and windows, I guess it’s time to evolve to the (somehow still obscure for me) UEFI and not to panic when BIOS becomes defunct. Even if I somehow manage to convert the disk to GPT and UEFI I’m not sure how I will configure the dual boot (currently GRUB takes care of that) but that’s theme for another question