What command line command would I use to run Software and Upgrades tool, mine isn't running from icon.
(wrong answer - deleted for "clairity")
Yes, but my problem is I need to get into the settings and turn on software sources that was turned off during the upgrade.
Yes that is exactly what I need to open and edit.
Good luck with these suggestions but, as far as I can tell, doing ANY updates to ubuntu-mate-20.10-desktop-arm64+raspi.img will eventually break the update mechanisms (and worse). Best to disable all updates in the GUI app upon installing the image and use only "sudo apt update/upgrade" after a dd image backup when absolutely necessary.
The builtin update app has sent every attempt at running this image off the rails for me. Latest symptom is that Software and Upgrades tool fails to start from GUI and running software-properties-gtk gives this:
ERROR:dbus.proxies:Introspect error on :1.165:/: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
Traceback (most recent call last):
..... hundred more lines of python errors!!!
Once this started occurring the image was completely broken in other ways. Simple attempt to edit a file gives this:
$ vi anyfile
Segmentation fault (core dumped)
Before all of this there were cases where corrupted *.list files made all update attempts fail. Had to google/hack a script to add '\n' to the bad files but only got a few hours more use before the above.
Please developers, stop working on unnecessary features and make the update mechanism failsafe.
After my next restore from backup I will try "apt remove update_manager software-properties-gtk" and see if things go better. My Pi is an 8GB Pi 4.