Learning to use Ubuntu Linux can take a day, or less if you have some experience with other operating systems like Windows, Mac, and other Linux based Operating systems like Fedora, OpenSuse, Puppy Linux, and Linux Mint.
If you know how to install Windows or another Linux operating system, installing Ubuntu Linux should be pretty simple, or even more simpler since the desktop install liveCD for Ubuntu is very well documented, and ask you questions on how to set up your computer, and user account for Ubuntu.
Buying a computer or laptop, pre-installed from System76.com , can make learning Ubuntu easier since you don’t have to deal with hardware incompatibilities related to Ubuntu and computer hardware which you may encounter when installing Ubuntu yourself on a store bought PC which was built for Windows and Mac, but not for Ubuntu Linux. You can also always phone or e-mail System76 if you have Ubuntu Software or Hardware related problems related to your System76 computer. System76 computers maybe more expensive, but they use higher quality computer parts, and provide good technical supports for their computers which all use Ubuntu Linux/
Note: I’m not affiliated with System76, but I am a fan of their computers, and want to buy one of their desktops or laptops someday.
Keeping Ubuntu Linux updated is simple as well since the Update manager informs you when new updates are released, or you can check manually by opening the update manager by clicking on the shortcut in the launcher or menu, and click check and install updates.
If you know how to use FireFox, OpenOffice, Gimp image editor, Media Players, and other software for Windows, or Mac, learning the Ubuntu versions of these software should not take too long to learn because the user interfaces, are the same, or very similar most of the time.
There is also a lot of websites, forums, books, YouTube Channels, videos, and user groups dedicated to teaching computer beginners on learning how to use Ubuntu Linux as their daily operating system for web browsing, e-mail, chat, multimedia, and gaming.
I recommend Official Ubuntu Book, The (6th Edition) if you are in need of a book which teaches you how to use Ubuntu Linux as your daily operating system for doing basic everyday task, and more advance tasks.
For absolute beginner computer users, it would probably take a few weeks, or a few months to learn how to use Ubuntu if you watch videos/DVDs, and read books about how to use Ubuntu Linux as your daily operating system. Although, learning how to use the monitor, mouse, speakers, microphone, and keyboard might take longer for people who never touched a type writer or anything similar to a PC in their whole life.
In some ways, learning how to use Ubuntu is easier then Windows since you don’t have to learn about how to use and subscribe anti-virus, anti-spyware, anti-malware, firewall, disk cleanup, disk defrag, and registry cleaner software which are only needed in Windows computers, but are not needed in Ubuntu Linux since all the software in the “Ubuntu Software Center” should be virus free, Ubuntu does not need a firewall in most cases for most users, Ubuntu does not suffer from lack of free space, or disk fragmentation, and Ubuntu does not need or have a registry like Windows.