Maybe you can refer to the Docker On i.MX6UL With Ubuntu16.04 - NXP Community
At the beginning of this document. It introduces how to install arm ubuntu.
Hi @Xelfiera,
We don’t have any official support for this distribution. You can review the official platforms that Cannonical offers official support at the following link:
Have a great day!
Do not understand what you are talking about. Do not understand why you need to change the ubuntu rootfs for Raspberry.
Why in your view, a ubuntu rootfs is related to a certain device.
A certain device is related to Linux kernel, not rootfs.
The way, the document introduces to create ubuntu rootfs can be run on any arm device.