Important: do this after installing Adrenalin 26.8.1.

Don't enable the block before installing 26.8.1, because the policy can also prevent a driver from being installed manually.

1. Install 26.8.1 first.

Do your:

DDU → Safe Mode → Clean AMD drivers → reboot → install Adrenalin 26.8.1

Get the GPU working normally first.

Then:

Win + X → Device Manager → Display adapters → Your GPU

Right-click → Properties → Details tab.

Change Property to:

Hardware IDs

You'll see something similar to

PCI\VEN_1002&DEV_747E&SUBSYS_... 
PCI\VEN_1002&DEV_747E

Take note of the topmost entry and the 2nd entry.

2. Open Group Policy Editor

Press:

Win + R

Type:

gpedit.msc

Press Enter.

Go to:

Computer Configuration → Administrative Templates → System → Device Installation → Device Installation Restrictions

3. Enable the GPU-only block.

Find:

Prevent installation of devices that match any of these device IDs.

Double-click it.

Select:

Enabled

Then click:

Show...

Enter your GPU hardware ID:

Click:

OK → Apply → OK

DO NOT enable these:

❌ Prevent installation of devices using drivers that match these device setup classes.
❌ Prevent installation of devices not described by other policy settings
❌ Prevent installation of removable devices

It means you have to open these policies and select "disable" instead of "default."

We only want the specific AMD GPU hardware ID.

4. VERY IMPORTANT—leave this unchecked.

When you open the policy's options, there may be:

Also apply to matching devices that are already installed.

Leave that UNCHECKED.

You don't want to block the currently functioning GPU itself. Microsoft specifically warns that retroactive prevention can affect already-installed devices.

Your goal is

Current 26.8.1 driver = allowed to remain installed

Future Windows Update AMD GPU driver = blocked

5. Force the policy to apply.

Open Command Prompt as Administrator and run:

gpupdate /force

You should get:

The computer policy update has been completed successfully.

Then reboot.

6. Verify it.

After reboot:

Device Manager → Display adapters → YOURGPU → Properties → Driver

Check that you're still on the AMD driver you installed with 26.8.1 or 32.0.31041.1004, which is the exact Windows Driver Store version included with AMD Adrenalin 26.8.1.