In your case, you can try disabling Secure Boot in the laptop's BIOS. Then, try disabling Driver Signature Enforcement again and see if you can install an older AMD driver.
If you need help disabling Secure Boot, please share a picture of your laptop's BIOS screen.
It's fine if it's taken with a camera or smartphone. It just needs to be clear.
Let me know the result. Click on the "Reply" button below my reply.
Feel free to ask back any questions.