If you want a portable Lubuntu system, there is a new, easy and reliable way to do it. The method should work for all Ubuntu family desktop systems and you can make your own system too, for example with a very light-weight desktop environment or simple window manager like Fluxbox.
You can start from an official Ubuntu Server compressed image file (so far only for Kinetic Kudu to be released as 22.10), and you get a system that boots most computers both in UEFI mode and BIOS mode (alias CSM alias legacy mode). But as usual, computers that need proprietary drivers (e.g. for graphics or wifi) will have problems or create problems for other computers, in other words: limit the portability between computers.
You ‘only’ have to install the meta package
lubuntu-desktop. See more details at this link: