[SIZE=4]Edit: Stable portable systems[/SIZE]
If you want a stable portable system, that boots in UEFI mode as well as BIOS/CSM mode, and in 64-bit as well as 32-bit computers, you can try
One pendrive for all PC (Intel/AMD) computers.
If you want a pendrive with a live and an installed system, that works in UEFI and BIOS mode, you can try
Compressed image file with a live Ubuntu 14.04.2 and an installed Ubuntu 15.10
I have developed a system from Ubuntu Xenial amd64 (I call it gamma because it is beyond beta), and I was able to simplify the method to make a stable installed system for UEFI and BIOS mode. See this link
with a description how to make it 'from scratch' plus a link to where I have uploaded compressed image files plus a small script to fix the GPT after cloning.
Two updated 'text-mini' compressed image files are uploaded 2016-05-27
There is a new stable alternative with Lubuntu 18.04.1 LTS. It provides live, persistent live and installed systems for one single USB pendrive (size at least 16 GB).
See more details at post #187 and the following link to an Ubuntu help page,
help.ubuntu.com/community/Installation/UEFI-and-BIOS/stable-alternative-18.04.1
[HR][/HR] Get and overview at the following Ubuntu help wiki page: **help.ubuntu.com/community/Installation/UEFI-and-BIOS**
[HR][/HR] [size=3]There is a torrent file that you can use to build your own custom operating system[/size]
The dd_text_16.04-UEFI-n-BIOS compressed image file was made up to date, and a torrent file was uploaded in January 2017. It can be used, if you want to start with a light-weight system and install your own selection of program packages - desktop packages, server packages and application packages.
dd_text_16.04-UEFI-n-BIOS_2017-01-15_intel-4-pendrive-7.8GB.img.xz.torrent
Use *mkusb* to install from the downloaded compressed image file to a USB pendrive, a memory card, or maybe an external SSD or HDD.
See details at this link: Installation/UEFI-and-BIOS/torrent
[HR][/HR] [size=3]Detailed description of the original installed system[/size]
I wanted an installed system as a good alternative to a persistent live system that boots new computers with and without UEFI. So I made one, which is described in this link
https://help.ubuntu.com/community/Installation/UEFI-and-BIOS
But I have tested it in only two computers, my Toshiba laptop, where I made it, and in my son's HP Elitebook laptop, so I don't know how portable it is.
The method is described in detail, and there is a compressed image of an Ubuntu 12.04.4 system available at
http://phillw.net/isos/linux-tools/uefi-n-bios
I think the *method* is at least as important to test as the compressed image, if and how it works in other computers.
So now, that we have finished testing beta 2, maybe there is time for you to try the method and make an UEFI-and-BIOS pendrive with your favourite flavour of Ubuntu Trusty beta 2.
*Not stable enough to survive certain updates*
I expected that this 'Portable installed system that boots in UEFI as well as in BIOS mode' could be installed into a USB pendrive as a good alternative to a persistent live system, possible to update and upgrade without limits. But unfortunately a current update involving a new kernel and updating grub will make it fail to boot. So this system is not stable enough to survive certain updates. It is good only as an illustration of a method to make a bootable drive in UEFI as well as BIOS mode.
*Links*
It might be a good idea to try various systems and methods before deciding what to install. Try Ubuntu (Kubuntu, Lubuntu, Xubuntu, ...) before installing it
The following links contain general information https://help.ubuntu.com/community/Installation/FromUSBStick https://help.ubuntu.com/community/DiskSpace