After installing Armbian_23.2.1_Rock-5b_bookworm_legacy_5.10.160_xfce_desktop.img I found a nagging error each start of Firefox.
"Failed to read the configuration file. Please contact your system administrator."
Looking at internet with Google I found hardly any link referring to linux or armbian, therefore I still don't know which configuration file was actually missing or damaged.
The only link I found with armbian in it contained some very obscure editting of some configuration files (just like many proposed Windows solutions).
The issue: where does it go wrong?
The problem is some configuration clutter somewhere in /usr/lib/firefox-esr.
And how to solve?
A Windows video showed a user removing and reinstalling firefox. Reinstalling with a blank configuration really does solve this problem (try as root or use sudo):
apt --purge remove firefox-esr
rm -rf /usr/lib/firefox-esr
apt install firefox-esr
I guess only users who don't use a minimal image may encounter this problem.