check the default web browser using
xdg-settings --list
xdg-settings get default-web-browser
echo $BROWSER
If you want to change the Chrome to Firefox and your default-web-browser
is already Firefox,
then you have to check the .config/mimeapps.list
[Default Applications]
x-scheme-handler/http=firefox.desktop
x-scheme-handler/https=firefox.desktop
x-scheme-handler/ftp=firefox.desktop
x-scheme-handler/chrome=firefox.desktop
text/html=firefox.desktop
application/x-extension-htm=firefox.desktop
application/x-extension-html=firefox.desktop
application/x-extension-shtml=firefox.desktop
application/xhtml+xml=firefox.desktop
application/x-extension-xhtml=firefox.desktop
application/x-extension-xht=firefox.desktop