Run the following 3 cmds in a terminal
sudo mv /etc/apt/sources.list.d/3cxpbx.list.save /home/administration/Desktop
sudo apt-get --purge remove appstream
wget -O-
http://downloads-global.3cx.com/downloads/3cxpbx/public.key | sudo apt-key add -
Take another snapshot and name it - Changes pre reboot
Reboot the "Machine" (Guest)
**Check the Software and Updates to ensure all the boxes are ticked. I found mine were not so the upgrade failed to action and had to redo the previous step***
in a terminal
sudo apt-get update
sudo apt-get upgrade
Take another Snapshot and name it - Upgraded pre Dist upgrade (I also included the cmds I'd used in the description, just in case)
sudo apt-get dist-upgrade
Take another Snapshot and name it - Dist upgraded pre reboot
sudo reboot
In a terminal:
sudo apt-get --purge autoremove cleans out the rubbish
hostnamectl Tells me if upgraded
So now I am running Debian 10 A few extra steps for safety, namely the creation of a lot of Snapshots, but they only take 10 seconds each and can be deleted afterwards.
For some reason, 3CX didn't seem to be installed, but simply in a terminal
sudo apt-get install 3cxpbx
and it was installed and had all my settings