Support for Windows 8.1 has been discontinued long before Windows 7. I do not know if you are aware of this, but Microsoft has dropped feature updates for Windows 8.1 I think in 2017 already, although they still release security updates.
The last driver AMD released for Windows 8.1 was version 17.7.1 which you can still download and is ironically the last driver that contained great performance for Unreal Engine 3 DirectX 9 games for Radeon cards.
This is the link to the last supported Windows 8.1 driver: https://www.amd.com/en/support/kb/release-notes/rn-rad-win-17-7-1
Overall, upgrading to Windows 10 might be the best choice, depending on if you want to play DirectX12 games.
Edit: Do you have Windows 8.1? It might still be compatible with most applications, you are just going to miss the latest driver features and optimizations, and some newer games require DirectX12 from Windows 10.
I'm planning to upgrade to Windows 11 when it's released. Windows 8.1 is available for upgrade to Windows 11. Thanks for the information.
Edit: There is a way to Install AMD Radeon Drivers on Windows 8.1: https://community.amd.com/t5/drivers-software/adrenalin-2020-on-windows-8-1/td-p/122955