I installed Ubuntu 20.04 LTS with the 5.11.0-34-generic kernel on my mid-2009 macbook pro which has nvidia geforce 9400M graphics hardware. Suspend and wake from suspend does not work with the nouveau open source graphics driver, so I wanted to install the nvidia proprietary graphics driver. The nvidia driver available within 'Additional Software' is the correct version for my machine, but it doesn't support the 5.11 kernel, so I installed the patched nvidia driver for my machine using the following from https://launchpad.net/~kelebek333/+archive/ubuntu/nvidia-legacy:
sudo add-apt-repository ppa:kelebek333/nvidia-legacy sudo apt update sudo apt install nvidia-340 sudo reboot
This enabled suspend and wake from suspend perfectly, but had the undesirable side effect of disabling the LCD brightness controls from both the macbook pro keyboard shortcut keys (F1 and F2), from the desktop GUI controls, and from settings. The keyboard backlight controls and volume controls all still work. LCD brightness controls had previously worked 'out of the box' with the nouveau graphics driver.
Would appreciate advice on how to get LCD backlight control functionality back after installing the nvidia driver.