In the past with BIOS, I've never created a separate partition for the bootloader.
My question is, if i wish to use UEFI, is a separate boot partition a requirement?
PS, I've tried without and it doesn't seem to work. Hence this question.
Yes, a separate EFI partition (FAT32 formated) small partition is always required if using UEFI mode. ~300MB should be enough for multi-boot but ~550MB is preferable.
The ESP - EFI System Partiton - should not be confused with
/boot (not required for most Ubuntu installations) and is a standard requirement.