Gfilui

I've bought new Dell 5570 i5 8250u 4GB RAM 1TB HDD AMD 530 2GB and it came with Ubuntu pre-installed.

After typing sudo lshw -class display I got:

description: VGA compatible controller

 product: Intel Corporation
 vendor: Intel Corporation
 physical id: 2
 bus info: pci@0000:00:02.0
 version: 07
 width: 64 bits
 clock: 33MHz
 capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
 configuration: driver=i915_bpo latency=0
 resources: irq:280 memory:d1000000-d1ffffff memory:b0000000-bfffffff ioport:f000(size=64)

Also, lspci gives me

00:00.0 Host bridge: Intel Corporation Device 5914 (rev 08)
00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev 07)
00:04.0 Signal processing controller: Intel Corporation Skylake Processor Thermal Subsystem (rev 08)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:15.0 Signal processing controller: Intel Corporation Sunrise Point-LP Serial IO I2C Controller #0 (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
00:17.0 RAID bus controller: Intel Corporation 82801 Mobile SATA Controller [RAID mode] (rev 21)
00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1)
00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #5 (rev f1)
00:1c.5 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #6 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Device 9d4e (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Device 9d71 (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
01:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Topaz XT [Radeon R7 M260/M265 / M340/M360 / M440/M445] (rev ff)
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller (rev 07)
03:00.0 Network controller: Qualcomm Atheros QCA9377 802.11ac Wireless Network Adapter (rev 31)

I'd like to change default gpu from intel hd 620 to discrete - AMD.

Is it possible?

You can use vga_switcheroo which allows you to switch between GPUs if your machine has a hardware mux.

To check whether your kernel is compiled with the correct option you can examine the file config-2.6.nn-mm-generic in the /boot directory :

grep -i switcheroo /boot/config-*

vga_switcheroo mechanism works when the kernel is booted with either the modeset=1 kernel option and/or the nomodeset option being absent. To test if vga_switcheroo is enabled, look for the switch file :

ls -l /sys/kernel/debug/vgaswitcheroo/switch

Using vga_switcheroo
If vga_switcheroo is available, you can switch between GPUs. Be prepared for something to go wrong and the system to lockup as the fact this file is there doesn't gaurantee the machine is supported.

Use this command to turn on the GPU that is currently disconnected, but it doesn't switch the outputs :

echo ON > /sys/kernel/debug/vgaswitcheroo/switch

This command connects the integrated graphics with the outputs :

echo IGD > /sys/kernel/debug/vgaswitcheroo/switch

This command connects the discrete graphics with the outputs :

echo DIS > /sys/kernel/debug/vgaswitcheroo/switch

This command turns off the graphics card that is currently disconnected :

echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

This command lets you check the current state of the hybrid graphics. There will usually be two lines of output - one should show Pwr and the other shows Off :

cat /sys/kernel/debug/vgaswitcheroo/switch

Note: This method is not supported by all system types and only works if you are using an open source driver (nouveau, radeon) and not the proprietary ones (nvidia, fglrx).

Source: https://www.dell.com/support/article/uk/en/ukbsdt1/sln298475/a-guide-to-hybrid-video-on-dell-pcs-with-an-ubuntu-operating-system?lang=en