Still not fixed for me.
$ kreadconfig5 --file kdeglobals --group General --key BrowserApplication firefox.desktop
$ xdg-settings check default-web-browser firefox.desktop /usr/bin/xdg-settings: 734: [: x!: unexpected operator no
Still not fixed for me.
$ kreadconfig5 --file kdeglobals --group General --key BrowserApplication
firefox.desktop
$ xdg-settings check default-web-browser firefox.desktop xdg-settings: 734: [: x!: unexpected operator
/usr/bin/
no