Ubuntu 20.04 on Asus ZenBook 14 UM433IQ-A5024 - Suspend does not work

I recently installed Ubuntu 20.04 on my new Asus ZenBook 14 UM433IQ-A5024. This is not my first time using Ubuntu but I am a relative beginner.

The problem: After being suspended, the laptop has some trouble to start again. The light on the ON switch keeps blinking, but the laptop takes a while to wake up. After starting again the background light of the keyboard does not work and the light on the Fn- key is inactive. If I try to turn the light on, the keys work. I get the graphical output on my screen, but the keyboard does not light up. Everything else seems to work fine.

I tried to look for others with a similar problem, but was not successful. I don't even know where to start looking and what could cause this problem, so any help is appreciated.

Thanks ahead!

I've managed to solve this issue in two Asus Notebooks, one Zenbook Q407I and a X441B model. In both cases the problem came from the kernel that comes out of the box with Ubuntu, version 21.10 in my case (the kernel version was 5.13).

Important! You may need to know a little about rebooting in recovery and rolling back some changes before doing this, because this might have helped me, but not all notebooks are the same.

The solution was to install the Mainline app following this tutorial: Mainline - Another Tool to Install Latest Kernel in Ubuntu / Linux Mint

1. To add the PPA, open terminal from system application launcher and run command:

   sudo add-apt-repository ppa:cappelikan/ppa
   

2. Then check updates and install the tool via commands:

   sudo apt update
   sudo apt install mainline
   

Then, after installing and running this app, my recommendation is to install the latest version of 5.14 kernel (5.15 won't install correctly because some dependencies aren't supported by Ubuntu yet). The GUI is pretty straightforward:

1. Click the version.
2. Install.
3. Wait until it succeeds.
4. After you reboot, Ubuntu will use the latest version of the kernel installed (in this case 5.14).

After doing this I was able to suspend/resume OK. This also fixed some problems with my sound card (it sounded like with very low quality in the Zenbook one) and brightness configuration persistence (brightness returned to lowest on every reboot).