Screen brightness only goes up to 20%; screen dims and flickers (XPS 13 -9370)

Laptop: XPS 13 -9370

• bios 1.11.1
• Display Adapter: intel UHD Graphics 620 (26.20.100.7212; khronos group 2019-09-12 )
• Monitor : Generic PnP Monitor (10.0.18362.207; Microsoft WinBuild 16101.0800)

_ Problem: The screen "brightness" slider-bar can only go up to 20%. When I adjust the brightness beyond 20%, the screen starts dimming and flickering.

I've been actively struggling with this problem and nothing is fixing the problem.

I've read and followed many posts on these boards (2019-09) and done the following ( ...multiple times, lol) : 

1) updated the following drivers :

un/re-installed via Device Manager

• Display Adapter : intel UHD Graphics 620
• Monitor - Generic PnP Monitor

Ran DELL's Suport Assist and everything updated :

• multiple FAILURES to install the "Intel Rapid Storage Technology Driver and Management Console"

   

  SWB,DRVR,IRST16.8.3,COMBO

  Version: 16.8.3.1003

  Category: Serial ATA

  Release Date: August 20, 2019

2) un-installed to previous version of Windows 10 (then reinstalled when I saw that nothing changed).

Currently running:

• Version1903 
• OS Build10.0.18362 
• Build Branch19h1_release

3) ran the Intel Drivers and Support Assistant, which updates drivers directly from Intel (graphics card, chipset)

• chipset
• video

I do not see on my computer, neither in the bios nor anywhere else, the control option available concerning "automatic-adjustment" of birghtness"; thus I cannot disactivate this option that some claim cause them problems.