They run Linux but you don’t need to know anything. They work out of the box. Guides are for upgrading to different user interfaces. You do need to learn how to make a copy of anl micro SD card because the ones that ship with the devices are extremely low quality and will quickly fail. I use the one from Raspberry Pi. It’s for installing pi OS but it does anything. www.raspberrypi.com/software/

Installing a different OS on a hand held is only picking a different image file like Knulli or GarlicOS when copying onto an SD card.