Can you see "Chipset" section of BIOS already? If not, please get images (F12 onto USB, or camera) of the BIOS, one showing all visible tabs/sections, and one each of the following Main, Advanced, Boot, security and save & Exit.
This can be done via BIOS mod to enable the chipset section for you hopefully, or it can be done by booting to grub and changing a few settings. If your laptop does not have USB Flashback feature, then you will be booting to grub anyway in order to unlock BIOS Lock so you can flash the modified BIOS with FPT.
If you are familiar with grub and setup_var already, following settings are all you need to change, and here's a general guide for another purpose, but it will get you booting to grub if you follow along. This guide is for unlocking the BIOS Lock mentioned above to flash modified BIOS, but use in same way for below variables)
https://www.win-raid.com/t3908f16-GUIDE-...-BIOS.html
Primary Display, VarStoreInfo (VarOffset/VarName):
0x7F8 << This variable used to change this setting
One Of Option: Auto, Value (8 bit): 0x3 {09 07 8D 00 00 00 03}
One Of Option: IGFX, Value (8 bit): 0x0 {09 07 49 05 00 00 00}
One Of Option: PEG, Value (8 bit): 0x1 (default) {09 07 4A 05 30 00 01} << This is default value 0x1
One Of Option: PCI, Value (8 bit): 0x2 {09 07 4B 05 00 00 02}
One Of Option: SG, Value (8 bit): 0x4 {09 07 4C 05 00 00 04} << This is one you need to change to 0x4
So, grub command >>
Setup_Var 0x7F8 0x4
And this is next setting you need to change
Internal Graphics, VarStoreInfo (VarOffset/VarName):
0x7FE
One Of Option: Auto, Value (8 bit): 0x2 {09 07 8D 00 00 00 02}
One Of Option: Disabled, Value (8 bit): 0x0 (default) {09 07 8F 00 30 00 00} << Default 0x0
One Of Option: Enabled, Value (8 bit): 0x1 {09 07 8E 00 00 00 01} << Change to 0x1
So, grub command >>
Setup_Var 0x7FE 0x1