From live 32-bit Kubuntu, I'm trying to install over Ubuntu 14 on older MacBook Pro. Everything seems good until disk partitioning, when auto-install gives a message warning there may be troubles without EFI partition. Ubuntu 14 has run without problem, when lack of EFI was presumably not a problem. How should partitions be for a good Kubuntu 18 install? Can this be done within installer, or by some other means?
UEFI systems require an ESP (EFI System Partition) to boot, however Legacy/BIOS does not require ESP. You will need to find out whether your machine boots via UEFI or BIOS (Google search may help?). If you need an ESP, and the installer will not create one for you, it should be around 500MB in size. This being said, if the installer says you need an ESP, it is most likely correct.