Disable LCD brightness control in MATE

I have Debian 12 with MATE 1.26.0 running on a Dell D620. My laptops firmware and MATE fight over backlight brightness control, either conflicting or doubling actions with the keyboard shortcuts. When in the BIOS, a TTY, or a stand alone window manager, the brightness keys works as they should. But in a MATE session, a brightness indicator comes up on screen and sometimes acts erratically as both MATE and the laptop are controlling the brightness at the same time.

I've searched through dconf editor and the keyboard shortcuts in MATE, but can't find anyway to disable control. Any ideas?