I have just checked the last image Armbian Bookworm with Gnome Desktop and this one has a firefox.conf located in /etc/armbian . So the problem is solved for the Gnome Desktop and Cinnamon Interfaces. I was looking for an XFCE interface, so I picked one in the archives and those one have the problem of the firefox.conf file missing.
So the problem is solved for the new releases and this topic can be closed.