How to create a bootable usb of othe OS on Endless?

I need to install an Ubuntu on my PC, please help!

It does not have startup disc creator or other app of this kind here

I suggest using Etcher [https://etcher.io]
It is very easy to use and multi platform

Endless OS comes with Disks, which can write ISO images verbatim to USB. I believe Ubuntu ISOs work if written like this.

Use the “Disks” utility to write the Ubuntu ISO to a USB, as described here (should work for Ubuntu ISO the same): https://support.endlessm.com/hc/en-us/articles/210654503-How-do-I-create-an-Endless-USB-stick-from-Linux-

Windows USB sticks cannot be loaded at booting. Disks cannot create a proper Windows USB stick. That’s a problem.