Ubuntu – Brightness Alters between 0 and 100

I have recently installed Ubuntu 18.04 for the very first time. Unfortunately, I am having problems with the brightness controls in Linux. What further compounds my problem is that I have not found any posts that have helped with my current predicament.

Here's what doesn't work:

• The brightness slider. It is there, and I can slide it around, though nothing happens to the brightness.
• xbacklight. I have also installed xbacklight in an attempt to change the brightness. However, no matter what value I set the brightness to, my real screen brightness stays at 100%. If I set it to 0%, it does completely dim my screen, but if I set it to 1%, -get outputs "1", though my real screen brightness is still at 100%.
• The fn keys for brightness are a bit glitchy. The default keys for brightness control are fn+f5 (to increase brightness) and fn+f6 (to decrease it). Attempting to increase brightness has a chance of increasing the volume of my internal microphone (upon inspection of keyboard shortcut settings, I have found no control options for microphones), and attempting to decrease it brings about a chance to mute my internal microphone.

Here's what I've tried:

• Editing GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"in /etc/default/grub. I have also previously set the value of acpi_backlight to video, to no avail.
• sudo-prime intel

• Altering /usr/share/X11/xorg.conf.d/80-backlight.conf with the following content:

  Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "AccelMethod" "sna"
Option "Backlight" "acpi_video0"
BusID "PCI:0:2:0"
EndSection

• Altering /usr/share/X11/xorg.conf.d/20-intel.conf with the following content:

  Section "Device"
Identifier "card0"
Driver "intel"
Option "Backlight" "intel_backlight"
BusID "PCI:0:2:0"
EndSection

• Changing my "Additional Drivers" settings to as depicted in the image
  here (Essentially, using nvidia-driver-435 and not using Intel).

My Laptop's specifications:

• Lenovo Legion Y740
• Intel® Core™ i7-9750H CPU @ 2.60GHz × 12
• Intel® UHD Graphics 630 (Coffeelake 3×8 GT2)
• NVIDIA RTX 2060

It would help me tremendously should somebody have a working solution to my problem, as the brightness gets quite intrusive at night. I would really appreciate any suggestions I can get, and I apologize for my really long post.