Hello,
since I am a friend of clonezilla and I use it to back up all my other devices including my server, let me give you a solution based on rufus to write clonezilla to a usb stick:
Download the ISO of clonezilla:
http://www.clonezilla.org/downloads/download.php?branch=alternative
I took i386. In principal you can use the standard iso, but I like to have the most vanilla version.
Further I use rufus to write the iso to a usb stick
https://rufus.akeo.ie/
I use the the parameters in the attached screen capture.

Then, while you boot press ESC on your OTG keyboard.
Go to the last menu entry on the right, on the bottom you have an option, besides Android IA and Windows. That is the one to use.
The rest is IMHO self explanatory.
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