Every time ubuntu starts the screen, the maximum brightness problem is solved.

Have you tried this method?

First, make sure that this file is available:

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/Sys/class/backlight/acpi_video0/brightness

The cat value is your current screen brightness.
Modify the following file to add some user startup settings:

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Sudo gedit/etc/rc. local

Add the following code above exit 0 (make sure exit 0 is not commented out ):

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Echo screen brightness value>/sys/class/backlight/acpi_video0/brightness

In this way, the file will be read at the end of the boot to dynamically write the screen brightness value to the brightness file to change the current brightness.

The following method is similar to the preceding one, but you can use it.

After entering the system, adjust the appropriate brightness and then query the value of the brightness,

Follow these steps:

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$ Cat/sys/class/backlight/intel_backlight/brightness 976 $ Sudo vim/etc/rc. local

 
# Add the following command to display the adjusted brightness next time you start the system.

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Echo 976>/sys/class/backlight/intel_backlight/brightness

If the preceding statement is invalid, change brightness to actual_brightness.

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/Sys/class/backlight/intel_backlight/actual_brightness