[NAME]   Root cause is intel driver as main display is powered by onboard intel graphics Download DDU ( Display Driver Uninstaller )  Reboot to safe mode  Run DDU and wipe out both drivers.  Let the machine boot to OS, this should fix it    In order to get Brightness controls back you will have to install dell recommended driver  Link  [URL]  
HiMy Dell Inspiron 5459 was giving flickering issues. I have got the display cable changed and since then facing very peculiar issue.When the Intel Graphics 520 is enabled, the display in BIOS (Dell splash logo) remains in laptop screen, but immediately once system enters WIN 10, laptop screen blacks out but lights, fan are working. I happened to connect an HDMI cable to external monitor, only to realise the display moves to the external monitor, while the laptop screen is still blank....Also, some other observations:- No option to adjust brightness slider in windows- No option to extend/ duplicate screenThis makes be believe it is a software issue, not hardware.The only fix I seem to find is in 2 situations:SAFE MODE BOOTDISABLE INTERL GRAPHCS 520 IN DEVICE MANAGERIve tried updating both the drivers for Intel and AMD, resetted Windows but nothing works. Below is the system info.Many thanksAnujOS Name Microsoft Windows 10 EnterpriseVersion 10.0.19043 Build 19043Other OS Description Not AvailableOS Manufacturer Microsoft CorporationSystem Name ANUJSystem Manufacturer Dell Inc.System Model Inspiron 5459System Type x64-based PCSystem SKU 06B2Processor Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz, 2401 Mhz, 2 Core(s), 4 Logical Processor(s)BIOS Version/Date Dell Inc. 1.9.0, 07-09-2020SMBIOS Version 2.8Embedded Controller Version 255.255BIOS Mode UEFIBaseBoard Manufacturer Dell Inc.BaseBoard ProductBaseBoard VersionPlatform Role MobileSecure Boot State OnPCR7 Configuration Elevation Required to ViewWindows Directory C:\WINDOWSSystem Directory C:\WINDOWS\system32Boot Device \Device\HarddiskVolume2Locale IndiaHardware Abstraction Layer Version = "10.0.19041.1151"Username ANUJ\DELLTime Zone India Standard TimeInstalled Physical Memory (RAM) 8.00 GBTotal Physical Memory 7.89 GBAvailable Physical Memory 6.12 GBTotal Virtual Memory 9.77 GBAvailable Virtual Memory 8.11 GBPage File Space 1.88 GBPage File C:\pagefile.sysKernel DMA Protection OffVirtualisation-based security Not enabledDevice Encryption Support Elevation Required to ViewHyper-V - VM Monitor Mode Extensions YesHyper-V - Second Level Address Translation Extensions YesHyper-V - Virtualisation Enabled in Firmware YesHyper-V - Data Execution Protection Yes
Black screen during Intel Graphics enabling