How to test the latest version of subiquity on PPC64LE / POWER System
detailing the infos from: 
https://discourse.ubuntu.com/t/how-to-test-the-latest-version-of-subiquity/12428


---------------------------------------------------------------------------------------
first option
---------------------------------------------------------------------------------------
1)
On petiboot menu - go to ` *Exit to shell`
    
 Petitboot (v1.7.5-p8f5fc86)                                   9006-12P 1302NXA
_______________________________________________________________________________
  [Network: enP2p1s0f0
    execute
    netboot enP2p1s0f0 (pxelinux.0)

  System information
  System configuration
  System status log
  Language
  Rescan devices
  Retrieve config from URL
  Plugins (0)
 *Exit to shell      

Exiting petitboot. Type 'exit' to return.
You may run 'pb-sos' to gather diagnostic data
#


2)
- From http://cdimage.ubuntu.com/ubuntu-server/focal/daily-live/current/
- Download the `PowerPC64 server .ISO image` (focal-live-server-ppc64el.iso) 
- Create a new dir and mount the image in 
/ # wget http://cdimage.ubuntu.com/ubuntu-server/focal/daily-live/current/focal-live-server-ppc64el.iso
focal-live-server-pp 100% |********************************|  934M  0:00:00 ETA
/ # mkdir iso
/ # mount -t iso9660 -o loop focal-live-server-ppc64el.iso iso


3)
- Load kernel and initrd from the loop-back mount: 
/ # kexec -l ./iso/casper/vmlinux -i ./iso/casper/initrd.gz 
/ # kexec -e


The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
...
done.
Begin: Running /scripts/init-premount ... done.
Begin: Mounting root file system ... Begin: Running /scripts/nfs-top ... done.
Begin: Running /scripts/nfs-premount ... done.
[    5.197384] EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null)
Begin: Running /scripts/casper-premount ... done.
done.


4)
- Few seconds later it will ask some questions:  
- Add again the .ISO URL : http://cdimage.ubuntu.com/ubuntu-server/focal/daily-live/current/focal-live-server-ppc64el.iso


Unable to find a medium container a live file system
Attempt interactive netboot from a URL?
yes no (default yes): 
Two methods available for IP configuration:
  * static: for static IP configuration
  * dhcp: for automatic IP configuration
static dhcp (default 'dhcp'): 
vlan id (optional): 
 http://cdimage.ubuntu.com/releases/focal/release/ubuntu-20.04-live-server-ppc64el.iso (default)
url: http://cdimage.ubuntu.com/ubuntu-server/focal/daily-live/current/focal-live-server-ppc64el.iso    
http_proxy (optional): 
Configuring networking...
Internet Systems Consortium DHCP Client 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/


5)
When it reachs the subiquity installer screen, 
On the top right - via the help menu - go to `enter shell`
- update the installer via: 

root@ubuntu-server:/# sudo snap refresh --edge subiquity

^ Latest version of subiquity will be downloaded and the installer will restart automatically.
Proceed with the installation.              

---------------------------------------------------------------------------------------
second option
---------------------------------------------------------------------------------------

On step 3) adding `subiquity-channel=edge` when loading kernel and initrd: 

/ # kexec -l ./iso/casper/vmlinux -i ./iso/casper/initrd.gz --append="subiquity-channel=edge"
/ # kexec -e
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
...

and on step 5)
When it reachs the subiquity installer screen, 
after you select a language 
it will show there's an update available: 

```
Version 20.07.1+git29.fc51315d of the installer is now available            
  (20.07.1+git2.5de9df3e is currently running).                               
                                                                              
  You can read the release notes for each version at:                         
                                                                              
               https://github.com/CanonicalLtd/subiquity/releases             
                                                                              
  If you choose to update, the update will be downloaded and the installation 
  will continue from here.   
                       [ Update to the new installer ]                       
                       [ Continue without updating   ]                       
                       [ Back                                                     
```                                                 

Select `Update to the new installer`
and then proceed with the installation.